restore APC hook for register serializer, fix #24
php_apc.c:1124:16: warning: variable 'h_files' set but not used [-Wunused-but-set-variable]
apc_cache.c:300:5: warning: pointer targets in passing argument 1 of 'php_stream_open_for_zend_ex' differ in signedness [-Wpointer-sign]
fix apc_serializers undefined
Merge pull request #25 from remicollet/issue-serializer

restore APC hook for register serializer, fix #24