drm: add libdrm_amdgpu (v7)

This is the new ioctl wrapper used by the new admgpu driver.
It's primarily used by xf86-video-amdgpu and mesa.

v2: fix amdgpu_drm.h install
v3: Integrate some of the sugestions from Emil:
    clean up Makefile.am, configure.ac
    capitalize header guards
    fix _FILE_OFFSET_BITS with config.h
    use drm_mmap/drm_munmap
    Remove unused ARRAY_SIZE macro
    use shared list implementation
    use shared math implementation
    use drmGetNodeTypeFromFd helper
v4: remove unused tiling defines
v5: include amdgpu.h in Makefile.am
v6: update amdgpu_drm.h
v7: libdrm.h -> libdrm_macros.h

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>