Move _GNU_SOURCE declarations to where it's used

Such that we don't rely on more GNU extensions accidentally.

perf/Makefile.am

@@ -1,9 +1,4 @@
-# We're using _GNU_SOURCE to get the prototype for asprintf. This may
-# not be the most portable approach, but it is pragmatic and I'm
-# willing to do something cleaner as soon as it causes someone a
-# problem.
 INCLUDES =					\
-	-D_GNU_SOURCE				\
 	-I$(srcdir)				\
 	-I$(top_srcdir)/boilerplate		\
 	-I$(top_srcdir)/src			\

perf/cairo-perf-posix.c

@@ -53,6 +53,8 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#define _XOPEN_SOURCE 600	/* for round() */
+
 #include <signal.h>
 #include <sys/time.h>
 #include <unistd.h>

perf/cairo-perf.c

@@ -26,6 +26,8 @@
  *          Carl Worth <cworth@cworth.org>
  */
 
+#define _GNU_SOURCE 1	/* for sched_getaffinity() */
+
 #include "cairo-perf.h"
 
 #include "cairo-boilerplate-getopt.h"

test/Makefile.am

@@ -825,16 +825,10 @@ check-local:
 check_PROGRAMS =
 EXTRA_PROGRAMS =
 
-# We're using _GNU_SOURCE to get the prototype for asprintf. This may
-# not be the most portable approach, but it is pragmatic and I'm
-# willing to do something cleaner as soon as it causes someone a
-# problem.
 INCLUDES =					\
-	-D_GNU_SOURCE				\
 	-I$(srcdir)				\
 	-I$(srcdir)/pdiff			\
 	-I$(top_srcdir)/boilerplate		\
-	-I$(top_srcdir)/pixman/src		\
 	-I$(top_srcdir)/src			\
 	-I$(top_builddir)/src			\
 	$(CAIRO_CFLAGS)

test/cairo-test.c

@@ -23,6 +23,8 @@
  * Author: Carl D. Worth <cworth@cworth.org>
  */
 
+#define _GNU_SOURCE 1	/* for feenableexcept() et al */
+
 #if HAVE_CONFIG_H
 #include "config.h"
 #endif

test/invalid-matrix.c

@@ -24,9 +24,12 @@
  * Author: Carl Worth <cworth@cworth.org>
  */
 
+#define _ISOC99_SOURCE	/* for INFINITY */
+#define _GNU_SOURCE 1	/* for fedisableeexcept() et al */
+
 #include "cairo-test.h"
 
-#if _XOPEN_SOURCE >= 600 || defined (_ISOC99_SOURCE)
+#ifdef INFINITY
 #define HAVE_INFINITY 1
 #endif