msvc2005: more fixes for curl and libexpat

git-svn-id: svn://dev.exiv2.org/svn@3137 b7c8b350-86e7-0310-a4b4-de8f6a8f16a3
Default value for EXIV2_HTTP_POST

git-svn-id: svn://dev.exiv2.org/svn@3138 b7c8b350-86e7-0310-a4b4-de8f6a8f16a3