Split astobj2.c into more maintainable components.

Split astobj2.c into the following files to improve maintainability.

astobj2.c - object primitives, object primitive misc and initialization code.
astobj2_private.h - internal object declarations needed by the containers.
astobj2_container.c - generic conainer and container misc code.
astobj2_container_hash.c - hash container specific code.
astobj2_container_rbtree.c - rbtree container specific code.
astobj2_container_private.h - generic container definitions and rtti prototypes.

https://reviewboard.asterisk.org/r/3576/
........

Merged revisions 415317 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@415319 65c4cc65-6c06-0410-ace0-fbb531ad65f3