GitLab

    * remove unused mBufferMappings
    * warn when mapping multiple locations to same attachment
    * cap size for bufferMappings at GL_MAX_DRAW_BUFFERS
    * bind FBO before validate()

The shared and weak pointers are now included via ACGL.hh, this way there is one
one central place to replace the pointers if needed (C++11, TR1, boost, own variant).
For this, they are placed in a ptr namespace so std:: (C++11) and str::tr1:: (C++98)
variants as well as boost and own implementations can all get redirected.
C++11 detection added and correct non-tr1 header include added (should make VS2010
porting easier).

This patch hopefully fixes bug #233, but now we only have static registration of file types. In the future, we may have to find another solution for dynamic file type extensions by shared libraries (IO plugins).

* move mMode fom ArrayBuffer to VAO
* add attachAllAttributes method to VAO
* allow adding VAO attributes without binding them (location == -1)
* store state of previous VAO binding in static field