-mwin32 again

[Christopher Faylor <cgf at redhat dot com>]

I'm going through the sourceware directories adding logic for checking
if -mwin32 as needed.  It is required in, IMO, a surprising number of
cases.

Every time I add it, it feels wrong.  Many times I add it on a global
basis when it is needed for just one file, such as in the gdb
directory.

I really wish I could come up with some kind of heuristic in gcc that
says something on the line of "Oh, you're including windows.h?  In that
case, this is a windows file and I'll add blah/w32api to the include
search path."

There doesn't seem to be anything remotely like this in gcc but I was
wondering if anyone had any creative ideas for achieving this effect.

FYI, I've been adding something like the following to configure.in's
that need it:

case "${host}" in
*-*-cygwin*)
        touch ac$$.c
        if ${CC} -c -mwin32 ac$$.c >/dev/null 2>&1; then
            case "$EXTRA_CFLAGS" in
                *-mwin32*) ;;
                *) EXTRA_CFLAGS="-mwin32 $EXTRA_CFLAGS" ;;
            esac
        fi
        rm -f ac$$.o ac$$.c
        ;;
esac
AC_SUBST(EXTRA_CFLAGS)

I also have to add logic to Makefile.in that handles the "EXTRA_CFLAGS"
stuff.

cgf