Error out in configure if boost headers are missing

Change-Id: I9b9bec7c6decea44a4b0bd33edf6dc0066ee4414
Reviewed-on: https://gerrit.dechocorp.com/16556
Reviewed-by: Jenkins <hudsonbuild@mozy.com>
Reviewed-by: Wilson <weiminp@mozy.com>

configure.ac

@@ -28,7 +28,7 @@ AC_SEARCH_LIBS([clock_gettime], [rt])
 AC_SEARCH_LIBS([backtrace], [execinfo])
 AX_CHECK_OPENSSL
 AX_CHECK_ZLIB
-AX_BOOST_BASE([1.40])
+AX_BOOST_BASE([1.40],, [AC_ERROR([Missing boost headers (1.40+)])])
 AX_BOOST_PROGRAM_OPTIONS
 AX_BOOST_REGEX
 AX_BOOST_THREAD