msvcrt: Fix _stricmp behavior on characters that doesn't fit into signed char.

dlls/msvcrt/string.c

@@ -1766,7 +1766,7 @@ int __cdecl MSVCRT__strnicmp_l(const char *s1, const char *s2,
         MSVCRT_size_t count, MSVCRT__locale_t locale)
 {
     MSVCRT_pthreadlocinfo locinfo;
-    char c1, c2;
+    int c1, c2;
 
     if(s1==NULL || s2==NULL)
         return MSVCRT__NLSCMPERROR;

dlls/msvcrt/tests/string.c

@@ -2548,6 +2548,8 @@ static void test__stricmp(void)
     ok(ret > 0, "_stricmp returned %d\n", ret);
     ret = _stricmp("\xa5", "\xb9");
     ok(ret == 0, "_stricmp returned %d\n", ret);
+    ret = _stricmp("a", "\xb9");
+    ok(ret < 0, "_stricmp returned %d\n", ret);
 
     setlocale(LC_ALL, "C");
 }