(core) refactored 3dbase, the last of GL_HEADERS

All major paths have now been moved into the
agp layer. Some of the 3d cases are rather
untested, as is the validity of context- management
and launch_external / conservative mode.

Left for this branch now is some regression tests
for multitextured 3d model (i.e. box with
diffuse, text and normal), cleanup in agp/gl21 for
canvas resize and a gles2/gles3 update.