Increase default max number of headers

People have been running into the maximum number of headers limitation
more and more lately, so increase this a little bit.  It is a
per-thread overhead, so it should not make any real difference when it
comes to memory consumption.

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4422 d4fa192b-c00b-0410-8231-f00ffab90ce4

configure.ac

@@ -417,9 +417,9 @@ AC_DEFINE_UNQUOTED([VCC_CC],"$VCC_CC",[C compiler command line for VCL code])
 # Define HTTP_HDR_MAX_VAL
 AC_ARG_WITH(max-header-fields,
             AS_HELP_STRING([--with-max-header-fields=NUM],
-                           [How many header fields to support (default=32)]),
+                           [How many header fields to support (default=64)]),
             [],
-            [with_max_header_fields=32])
+            [with_max_header_fields=64])
 
 AC_DEFINE_UNQUOTED(HTTP_HDR_MAX_VAL, $with_max_header_fields, [Define maximum number of header fields supported by varnish ])