This patch fixes two warnings, enabling `-D_GNU_SOURCE` on GNU systems:

 * parse.y:296:29: warning: implicit declaration of function ‘asprintf’; did you mean ‘vsprintf’? [-Wimplicit-function-declaration]
 * parse.y:333:13: warning: implicit declaration of function ‘vasprintf’; did you mean ‘vsprintf’? [-Wimplicit-function-declaration]
---
 template/configure.ac | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/template/configure.ac b/template/configure.ac
index bd7a2184f..df2c739c8 100644
--- a/template/configure.ac
+++ b/template/configure.ac
@@ -5,6 +5,8 @@ AM_INIT_AUTOMAKE([foreign subdir-objects])
 AC_ARG_VAR(HOSTCC, [The C compiler on the host.])
 AC_ARG_VAR(HOSTCFLAGS, [CFLAGS for the host compiler])
 
+AC_USE_SYSTEM_EXTENSIONS
+
 # When CFLAGS isn't set at this stage and gcc is detected by the macro below,
 # autoconf will automatically use CFLAGS="-O2 -g". Prevent that by using an
 # empty default.
-- 
2.39.1