[PATCH:libXfont] Add AC_SYSTEM_EXTENSIONS to expose non-standard extensions

[Alan Coopersmith]

Required on Solaris to expose fd_mask in <sys/select.h> now that
xtrans 1.3 defines _XOPEN_SOURCE to 600 on Solaris, since fd_mask
is not defined in that version of the XPG standards.

Fixes build failure:
../../src/FSConnServ.c: In function '_FSWaitForWritable':
../../src/FSConnServ.c:166:6: error: 'fd_mask' undeclared (first use in this function)
../../src/FSConnServ.c:166:6: note: each undeclared identifier is reported only once for each function it appears in

Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
---
 configure.ac |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/configure.ac b/configure.ac
index e0e81bb..3591a1a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -29,6 +29,11 @@ AC_CONFIG_HEADERS([config.h include/X11/fonts/fontconf.h])
 # Initialize Automake
 AM_INIT_AUTOMAKE([foreign dist-bzip2])
 
+# Set common system defines for POSIX extensions, such as _GNU_SOURCE
+# Must be called before any macros that run the compiler (like
+# AC_PROG_LIBTOOL) to avoid autoconf errors.
+AC_USE_SYSTEM_EXTENSIONS
+
 # Initialize libtool
 AC_PROG_LIBTOOL
 
-- 
1.7.9.2