patch 8.0.0235: memory leak in diff mode

Problem:    Memory leak detected when running tests for diff mode.
Solution:   Free p_extra_free.
diff --git a/src/screen.c b/src/screen.c
index 016e7ee..e37bf48 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -3651,6 +3651,7 @@
 		{
 		    /* Draw the 'foldcolumn'.  Allocate a buffer, "extra" may
 		     * already be in use. */
+		    vim_free(p_extra_free);
 		    p_extra_free = alloc(12 + 1);
 
 		    if (p_extra_free != NULL)
@@ -4695,6 +4696,7 @@
 			p = alloc((unsigned)(len + 1));
 			vim_memset(p, ' ', len);
 			p[len] = NUL;
+			vim_free(p_extra_free);
 			p_extra_free = p;
 			for (i = 0; i < tab_len; i++)
 			{
@@ -4857,6 +4859,7 @@
 			vim_memset(p, ' ', n_extra);
 			STRNCPY(p, p_extra + 1, STRLEN(p_extra) - 1);
 			p[n_extra] = NUL;
+			vim_free(p_extra_free);
 			p_extra_free = p_extra = p;
 		    }
 		    else
@@ -5784,6 +5787,7 @@
     }
 #endif
 
+    vim_free(p_extra_free);
     return row;
 }
 
diff --git a/src/version.c b/src/version.c
index 8622e6d..65208d0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    235,
+/**/
     234,
 /**/
     233,