patch 8.2.0938: NFA regexp uses tolower ()to compare ignore-case
Problem: NFA regexp uses tolower() to compare ignore-case. (Thayne McCombs)
Solution: Use utf_fold() when possible. (ref. neovim #12456)
diff --git a/src/macros.h b/src/macros.h
index 16421d2..7604910 100644
--- a/src/macros.h
+++ b/src/macros.h
@@ -93,6 +93,7 @@
#define MB_ISUPPER(c) vim_isupper(c)
#define MB_TOLOWER(c) vim_tolower(c)
#define MB_TOUPPER(c) vim_toupper(c)
+#define MB_CASEFOLD(c) (enc_utf8 ? utf_fold(c) : MB_TOLOWER(c))
// Use our own isdigit() replacement, because on MS-Windows isdigit() returns
// non-zero for superscript 1. Also avoids that isdigit() crashes for numbers