This patch fixes the bug which makes 32-bit svnserve hang after some period of time
doing an infinite loop inside ensure_data_insertable() because cache->data_used becomes
a very big value, and ensure_data_insertable() never removes entries smaller than
cache->data_used / cache->used_entries / 8.

--- a/subversion/libsvn_subr/cache-membuffer.c	2014-02-12 21:42:12.483208244 +0000
+++ b/subversion/libsvn_subr/cache-membuffer.c	2014-02-12 21:45:54.275215290 +0000
@@ -1374,7 +1374,9 @@ membuffer_cache_set_internal(svn_membuff
    * the old spot, just re-use that space. */
   if (entry && ALIGN_VALUE(entry->size) >= size && buffer)
     {
-      cache->data_used += size - entry->size;
+      /* not "+=" because (size - entry_size) is almost always a big 32-bit
+         unsigned representation of a negative value on 32-bit platforms */
+      cache->data_used = cache->data_used + size - entry->size;
       entry->size = size;
 
 #ifdef SVN_DEBUG_CACHE_MEMBUFFER