Do not include <attribute.h> from <config.h>

Do not include <attribute.h> from <config.h>

This is because mod-test.c shouldn’t use source code from lib,
but it does need to include <config.h>.
* lib-src/ebrowse.c, lib-src/emacsclient.c, lib-src/etags.c:
* lib-src/make-docfile.c, lib-src/movemail.c:
* lib-src/seccomp-filter.c, src/dynlib.h, src/lisp.h:
* src/syssignal.h, src/sysstdio.h, src/systhread.h, src/tparam.h:
Include <attribute.h>.
* src/conf_post.h: Do not include <attribute.h>.
All uses of attribute.h macros replaced with their _GL_ equivalents.