This requires functions without a prototype definition to be static.
This allows to detect dead code, export less symbols and put shared
functions in headers.
This removes any assumptions about how the libdrm headers are installed,
and uses the pkg-config include directories as we're "supposed to".
This only adds a partial dependency, since we don't actually need to
link against libdrm.
Simon Ser
Scott Anderson
Rostislav Pehlivanov