Updated ph/CMakeLists: libxml2
Meta doubly linked-list API: base files, structures and macros
Meta doubly linked-list API: traversal macros
Meta doubly linked-list API: add front/back macros
Meta doubly linked-list API: erase macros
Meta doubly linked-list API: del front/back macros
Meta doubly linked-list API: for_each macros more reliable and syntax changed. Fixed a bug in DEL macros
Meta doubly linked-list API: pop front/back macros