patch 8.0.0689: ~ character not escaped when extending search pattern

Problem:    The ~ character is not escaped when adding to the search pattern
            with CTRL-L. (Ramel Eshed)
Solution:   Escape the character. (Christian Brabandt)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index ba8fde6..11de136 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -1492,7 +1492,7 @@
 			    if (c != NUL)
 			    {
 				if (c == firstc || vim_strchr((char_u *)(
-					      p_magic ? "\\^$.*[" : "\\^$"), c)
+					      p_magic ? "\\~^$.*[" : "\\^$"), c)
 								       != NULL)
 				{
 				    /* put a backslash before special