pp.c: Fix Win32 compilation problems

Commit 130c5df3625bd130cd1e2771308fcd4eb66cebb2 introduced errors into
Windows (at least) compilations because it used #if's in the middle of
apparent function calls, but these were really macros that turned the
function call foo() into a call of Perl_foo(), and so we were doing
an #if from within a #define which is not generally legal.
Fix some compilation warnings

After commits d6ded95025185cb1ec8ca3ba5879cab881d8b180 and
130c5df3625bd130cd1e2771308fcd4eb66cebb2, there are some compilation
warnings if not all locale categories are used.