Require C99

INSTALL

+============
+Installation
+============
+
 The most common installation procedure looks as follows.
 
 Unpack the tar archive and change into the unpacked directory.
 
   ./configure
   make check install
+
+
+=======================
+Intel compiler settings
+=======================
+
+The Intel compiler can improve performance by vectorizing certain
+parts of the code on x86 architectures.
+
+  ./configure CC=icc
+  make CFLAGS="-O3 -xCORE-AVX2"
+
+This assumes that you have a CPU which supports AVX2.

configure.ac

@@ -12,6 +12,7 @@ AM_INIT_AUTOMAKE
 
 # Checks for programs.
 AC_PROG_CC
+AC_PROG_CC_C99
 
 # Checks for libraries.
 AC_CHECK_LIB([aec], [aec_decode])