[babl] configure.ac: Fix the test for compiling half-floating point code.

[Michael Henning <mhenning src gnome org>]

commit 1a91a89ae942e1351c0c6ba624dd27c6dd7230f9
Author: Michael Henning <drawoc darkrefraction com>
Date:   Sun Jan 3 17:02:38 2016 -0500

    configure.ac: Fix the test for compiling half-floating point code.
    
    _mm_cvtph_ps is implicitly defined if the compiler does not support
    it. So, we need to store its return value in a variable so that
    the test fails to type check when the function is implicitly defined
    to return an int.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 28e9af0..e2ab5f7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -390,7 +390,7 @@ if test "x$enable_mmx" = xyes; then
 
         CFLAGS="$CFLAGS $sse_flag $f16c_flag"
 
-        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <immintrin.h>],[_mm_cvtph_ps 
((__m128i)_mm_setzero_ps());])],
+        AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <immintrin.h>],[__m128 val = _mm_cvtph_ps 
((__m128i)_mm_setzero_ps());])],
           AC_DEFINE(USE_F16C, 1, [Define to 1 if f16c intrinsics are available.])
           AC_MSG_RESULT(yes)
         ,