mathoms.c,utf8.c: Update to use UTF8_CHK_SKIP

This new macro expands to what these did.  Update to use the common
code.

1 files changed, 3 insertions, 2 deletions

diff --git a/mathoms.c b/mathoms.c
index b34012069f..b0122f95ca 100644
--- a/mathoms.c
+++ b/mathoms.c
@@ -1196,8 +1196,9 @@ Perl_is_utf8_char(const U8 *s)
     PERL_ARGS_ASSERT_IS_UTF8_CHAR;
 
     /* Assumes we have enough space, which is why this is deprecated.  But the
-     * strnlen() makes it safe for the common case of NUL-terminated strings */
-    return isUTF8_CHAR(s, s + my_strnlen((char *) s, UTF8SKIP(s)));
+     * UTF8_CHK_SKIP(s)) makes it safe for the common case of NUL-terminated
+     * strings */
+    return isUTF8_CHAR(s, s + UTF8_CHK_SKIP(s));
 }
 
 /*