Steps to reproduce:
1. use xmlNanoHTTPMethod with an URL like "http://localhost:1980"
   for example, use nd built against libxml2-2.6.31

I have found this bug using nd to connect to a webdav server listening on the 1980 port

Stack trace:
Building nd and libxml2 with debug symbols, without optimization and linking against efence:

Program received signal SIGSEGV, Segmentation fault.

+ Trace 188160

Other information:
before     bp = (char*)xmlMallocAtomic(blen); at line nanohttp.c:1352, you need to check if ctxt->port != 80, and add to blen the number of digits of ctxt->port + 1

A dummy patch resolve the bug:

diff -burN libxml2-2.6.31/nanohttp.c libxml2-2.6.31.fixed/nanohttp.c
--- libxml2-2.6.31/nanohttp.c   2007-08-28 19:34:00.000000000 +0200
+++ libxml2-2.6.31.fixed/nanohttp.c     2008-02-05 12:50:12.000000000 +0100
@@ -1339,6 +1339,15 @@
 #ifdef HAVE_ZLIB_H
     blen += 23;
 #endif
+       if (ctxt->port != 80) {
+               int test=ctxt->port;
+               while (test > 0) {
+                       test = test/10;
+                       blen++;
+               }
+               blen++;
+       }
+
     bp = (char*)xmlMallocAtomic(blen);
     if ( bp == NULL ) {
         xmlNanoHTTPFreeCtxt( ctxt );