ATTRIBUTE_HIDDEN for libbfd.h

[Tom Tromey]

>>>>> "Alan" == Alan Modra <amodra@gmail.com> writes:

Alan> 	* libbfd-in.h (ATTRIBUTE_HIDDEN): Define and use throughout.
Alan> 	* configure.ac (HAVE_HIDDEN): Check compiler support for hidden
Alan> 	visibility.
Alan> 	* libbfd.h: Regenerate.
Alan> 	* configure: Regenerate.
Alan> 	* config.in: Regenerate.

I noticed while testing patches on the gdb buildbot that this patch
seems to have broken the mingw build.

../../binutils-gdb/bfd/archive.c:187:1: error: visibility attribute not supported in this configuration; ignored [-Werror=attributes]


I can reproduce this on Fedora by installing the mingw toolchain and
then doing a build like:

../binutils-gdb/configure  --disable-{binutils,gas,gold,gprof,ld,sim} --host=i686-w64-mingw32 --target=i686-w64-mingw32 --enable-targets=all

Tom