Make sure that _GNU_SOURCE is enabled in the linux configs that set
HAVE_POSIX_MEMALIGN. This eliminates a compiler warning. Also,
clean up some crufty linux-sparc* configs.
diff --git a/configs/linux b/configs/linux
index 6736f14..0d455ff 100644
--- a/configs/linux
+++ b/configs/linux
@@ -17,7 +17,8 @@
ARCH_FLAGS ?=
DEFINES = -D_POSIX_SOURCE -D_POSIX_C_SOURCE=199309L -D_SVID_SOURCE \
- -D_BSD_SOURCE -DPTHREADS -DUSE_XSHM -DHAVE_POSIX_MEMALIGN
+ -D_BSD_SOURCE -D_GNU_SOURCE \
+ -DPTHREADS -DUSE_XSHM -DHAVE_POSIX_MEMALIGN
X11_INCLUDES = -I/usr/X11R6/include