Bug #7186: Fix an excessive request size limitation that broke big-requests.

MAXBUFSIZE appears to be a leftover of some previous time.  Instead, just
use maxBigRequestSize when bigreqs are available (limiting buffers to ~16MB).
When bigreqs are not available, needed won't be larger than the maximum
size of a non-bigreqs request (256kB).

os/io.c

@@ -304,12 +304,14 @@ ReadRequestFromClient(ClientPtr client)
 	 */
 
 	oci->lenLastReq = 0;
-	if (needed > MAXBUFSIZE)
+#ifdef BIGREQS
+	if (needed > maxBigRequestSize << 2)
 	{
 	    /* request is too big for us to handle */
 	    YieldControlDeath();
 	    return -1;
 	}
+#endif
 	if ((gotnow == 0) ||
 	    ((oci->bufptr - oci->buffer + needed) > oci->size))
 	{

os/osdep.h

@@ -55,9 +55,6 @@ SOFTWARE.
 #define BOTIMEOUT 200 /* in milliseconds */
 #define BUFSIZE 4096
 #define BUFWATERMARK 8192
-#ifndef MAXBUFSIZE
-#define MAXBUFSIZE (1 << 22)
-#endif
 
 #include <X11/Xdmcp.h>