unistd.h -vs- winnt.h

[Tom Tromey]

I tried to use gnulib more in gdb, but ran into issues with the mingw
port.

In particular one part of gdb uses gethostname.  So, I had to include
the gethostname module.

But, if I include that module, then the gnulib unistd.h can wind up
including <winnt.h>, which pulls in a lot of definitions that conflict
with symbols already defined elsewhere in gdb.  (And as you can imagine
from a tool that manipulates file formats, things like COFF details
defined in winnt.h conflict with similar definitions in BFD.)

So I get stuff like:

cp-name-parser.c:420:0: error: "VOID" redefined [-Werror]
In file included from 
/usr/i686-w64-mingw32/sys-root/mingw/include/windef.h:139:0,
                 from /usr/i686-w64-mingw32/sys-root/mingw/include/windows.h:69,
                 from 
/usr/i686-w64-mingw32/sys-root/mingw/include/winsock2.h:23,
                 from build-gnulib/import/unistd.h:34,
                 from ../../binutils-gdb/gdb/defs.h:53,
                 from ../../binutils-gdb/gdb/cp-name-parser.y:32:
/usr/i686-w64-mingw32/sys-root/mingw/include/winnt.h:192:0: note: this is the 
location of the previous definition


I can tell you how to grab the relevant gdb and build it if you want to
mess around.  It's straightforward.

Tom