Commit fix for CVE-2010-0010, an integer overflow on platforms where

Commit fix for CVE-2010-0010, an integer overflow on platforms where
sizeof(int) < sizeof(long) due to inappapriate casting;

    * Change "MIN( (int) a, (int) b)" to "(int) MIN(a, b)". As 'a' is the buffer
      size, it will be smaller than any long which overflows an int.

    * More generally - change ap_bread and ap_bwrite to defend against a negative
      length argument in general. Return -1 if one is passed.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@896842 13f79535-47bb-0310-9956-ffa450edef68