Add check for madvise(2) to configure.ac.
Some platforms, such as Google's Portable Native Client, use Newlib and
thus lack access to madvise(2). In those instances, pages_purge() is
transformed into a no-op.
diff --git a/configure.ac b/configure.ac
index 3d36b5f..29edcb6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1192,6 +1192,20 @@
fi
dnl ============================================================================
+dnl Check for madvise(2).
+
+JE_COMPILABLE([madvise(2)], [
+#include <sys/mman.h>
+], [
+ {
+ madvise((void *)0, 0, 0);
+ }
+], [je_cv_madvise])
+if test "x${je_cv_madvise}" = "xyes" ; then
+ AC_DEFINE([JEMALLOC_HAVE_MADVISE], [ ])
+fi
+
+dnl ============================================================================
dnl Check whether __sync_{add,sub}_and_fetch() are available despite
dnl __GCC_HAVE_SYNC_COMPARE_AND_SWAP_n macros being undefined.