patch 8.0.0520: using a function pointer while the function is known

Problem:    Using a function pointer instead of the actual function, which we
            know.
Solution:   Change mb_ functions to utf_ functions when already checked for
            Unicode. (Dominique Pelle, closes #1582)
diff --git a/src/message.c b/src/message.c
index a4dd746..a9a6669 100644
--- a/src/message.c
+++ b/src/message.c
@@ -315,7 +315,7 @@
 	for (;;)
 	{
 	    do
-		half = half - (*mb_head_off)(s, s + half - 1) - 1;
+		half = half - utf_head_off(s, s + half - 1) - 1;
 	    while (half > 0 && utf_iscomposing(utf_ptr2char(s + half)));
 	    n = ptr2cells(s + half);
 	    if (len + n > room || half == 0)
diff --git a/src/misc2.c b/src/misc2.c
index 2ded997..2f9fed5 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -1874,7 +1874,7 @@
     {
 	while (*p != NUL)
 	{
-	    int l = (*mb_ptr2len)(p);
+	    int l = utfc_ptr2len(p);
 
 	    /* Avoid matching an illegal byte here. */
 	    if (utf_ptr2char(p) == c && l > 1)
diff --git a/src/regexp.c b/src/regexp.c
index b4fe7d7..e1f6484 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -4732,7 +4732,7 @@
 		    break;
 		}
 		if (enc_utf8)
-		    opndc = mb_ptr2char(opnd);
+		    opndc = utf_ptr2char(opnd);
 		if (enc_utf8 && utf_iscomposing(opndc))
 		{
 		    /* When only a composing char is given match at any
@@ -4741,7 +4741,7 @@
 		    for (i = 0; reginput[i] != NUL;
 						i += utf_ptr2len(reginput + i))
 		    {
-			inpc = mb_ptr2char(reginput + i);
+			inpc = utf_ptr2char(reginput + i);
 			if (!utf_iscomposing(inpc))
 			{
 			    if (i > 0)
@@ -4750,7 +4750,7 @@
 			else if (opndc == inpc)
 			{
 			    /* Include all following composing chars. */
-			    len = i + mb_ptr2len(reginput + i);
+			    len = i + utfc_ptr2len(reginput + i);
 			    status = RA_MATCH;
 			    break;
 			}
diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index e6d8255..120861a 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -1974,7 +1974,7 @@
 nfa_do_multibyte:
 		/* plen is length of current char with composing chars */
 		if (enc_utf8 && ((*mb_char2len)(c)
-			    != (plen = (*mb_ptr2len)(old_regparse))
+			    != (plen = utfc_ptr2len(old_regparse))
 						       || utf_iscomposing(c)))
 		{
 		    int i = 0;
diff --git a/src/screen.c b/src/screen.c
index 6a7284b..ceb30e3 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -4119,7 +4119,7 @@
 		c = c_extra;
 #ifdef FEAT_MBYTE
 		mb_c = c;	/* doesn't handle non-utf-8 multi-byte! */
-		if (enc_utf8 && (*mb_char2len)(c) > 1)
+		if (enc_utf8 && utf_char2len(c) > 1)
 		{
 		    mb_utf8 = TRUE;
 		    u8cc[0] = 0;
@@ -4140,7 +4140,7 @@
 		    {
 			/* If the UTF-8 character is more than one byte:
 			 * Decode it into "mb_c". */
-			mb_l = (*mb_ptr2len)(p_extra);
+			mb_l = utfc_ptr2len(p_extra);
 			mb_utf8 = FALSE;
 			if (mb_l > n_extra)
 			    mb_l = 1;
@@ -4219,7 +4219,7 @@
 		{
 		    /* If the UTF-8 character is more than one byte: Decode it
 		     * into "mb_c". */
-		    mb_l = (*mb_ptr2len)(ptr);
+		    mb_l = utfc_ptr2len(ptr);
 		    mb_utf8 = FALSE;
 		    if (mb_l > 1)
 		    {
@@ -4612,7 +4612,7 @@
 		    }
 #ifdef FEAT_MBYTE
 		    mb_c = c;
-		    if (enc_utf8 && (*mb_char2len)(c) > 1)
+		    if (enc_utf8 && utf_char2len(c) > 1)
 		    {
 			mb_utf8 = TRUE;
 			u8cc[0] = 0;
@@ -4634,7 +4634,7 @@
 		    }
 #ifdef FEAT_MBYTE
 		    mb_c = c;
-		    if (enc_utf8 && (*mb_char2len)(c) > 1)
+		    if (enc_utf8 && utf_char2len(c) > 1)
 		    {
 			mb_utf8 = TRUE;
 			u8cc[0] = 0;
@@ -4765,7 +4765,7 @@
 			saved_attr2 = char_attr; /* save current attr */
 #ifdef FEAT_MBYTE
 			mb_c = c;
-			if (enc_utf8 && (*mb_char2len)(c) > 1)
+			if (enc_utf8 && utf_char2len(c) > 1)
 			{
 			    mb_utf8 = TRUE;
 			    u8cc[0] = 0;
@@ -4839,7 +4839,7 @@
 		    }
 #ifdef FEAT_MBYTE
 		    mb_c = c;
-		    if (enc_utf8 && (*mb_char2len)(c) > 1)
+		    if (enc_utf8 && utf_char2len(c) > 1)
 		    {
 			mb_utf8 = TRUE;
 			u8cc[0] = 0;
@@ -5003,7 +5003,7 @@
 		}
 # ifdef FEAT_MBYTE
 		mb_c = c;
-		if (enc_utf8 && (*mb_char2len)(c) > 1)
+		if (enc_utf8 && utf_char2len(c) > 1)
 		{
 		    mb_utf8 = TRUE;
 		    u8cc[0] = 0;
@@ -5110,7 +5110,7 @@
 		extra_attr = HL_ATTR(HLF_AT);
 	    }
 	    mb_c = c;
-	    if (enc_utf8 && (*mb_char2len)(c) > 1)
+	    if (enc_utf8 && utf_char2len(c) > 1)
 	    {
 		mb_utf8 = TRUE;
 		u8cc[0] = 0;
@@ -5383,7 +5383,7 @@
 	    char_attr = HL_ATTR(HLF_AT);
 #ifdef FEAT_MBYTE
 	    mb_c = c;
-	    if (enc_utf8 && (*mb_char2len)(c) > 1)
+	    if (enc_utf8 && utf_char2len(c) > 1)
 	    {
 		mb_utf8 = TRUE;
 		u8cc[0] = 0;
diff --git a/src/spell.c b/src/spell.c
index 1700bba..ed0db8c 100644
--- a/src/spell.c
+++ b/src/spell.c
@@ -1208,7 +1208,7 @@
 	/* Need to convert the single byte flags to utf8 characters. */
 	p = uflags;
 	for (i = 0; flags[i] != NUL; ++i)
-	    p += mb_char2bytes(flags[i], p);
+	    p += utf_char2bytes(flags[i], p);
 	*p = NUL;
 	p = uflags;
     }
@@ -5117,11 +5117,11 @@
 				 * SCORE_SUBCOMP. */
 				if (enc_utf8
 					&& utf_iscomposing(
-					    mb_ptr2char(tword
+					    utf_ptr2char(tword
 						+ sp->ts_twordlen
 							   - sp->ts_tcharlen))
 					&& utf_iscomposing(
-					    mb_ptr2char(fword
+					    utf_ptr2char(fword
 							+ sp->ts_fcharstart)))
 				    sp->ts_score -=
 						  SCORE_SUBST - SCORE_SUBCOMP;
diff --git a/src/version.c b/src/version.c
index 36adf25..5705d98 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    520,
+/**/
     519,
 /**/
     518,