crt: Fix strcmpi symbol alias for msvcr80-120 versions

msvcrt versions 8.0 - 12.0 and UCRT do not have _strcmpi symbol.

For these CRT versions (which have NO_STRCMPI_ALIAS) is later in the file
symbol _strcmpi defined as an alias to _stricmp symbol.

So for these affected CRT versions define strcmpi as an alias to _stricmp.

Signed-off-by: Martin Storsjö <martin@martin.st>