[waffle] [wflinfo] [RFC] platform-specific info from wflinfo

[Frank Henigman]

I'd like to extend wflinfo so it can print platform-specific
information and eventually be able to replace glxinfo, eglinfo and the
like (I only know what's on linux).  There would be a new flag to
request the platform-specific output in addition to the existing
output.  For example on glx you'd see glx extensions, on egl you'd see
egl extensions.
I've started two different implementations and I'd like to know which
is preferred before I go any farther.  Or if there's a better idea
than either of my approaches.  I've dubbed the two approaches "native"
and "core."

native
- all the work is done in wflinfo, no changes to waffle api
- use waffle_display_get_native() to access platform-specific stuff
- pro: changes limited to wflinfo, doesn't clutter up the rest of waffle
- con: some duplicate code to open libraries and lookup symbols
- https://github.com/fjhenigman/waffle/tree/ps_native

core
- add waffle_display_print_info() to waffle api
- add print_info() method to each platform
- pro: less code, no duplication
- con (perhaps): some wflinfo functionality is now in core waffle
- https://github.com/fjhenigman/waffle/tree/ps_core

I'm leaning toward "core" because there is less code.  We get to
leverage the platform libraries and functions already stored in waffle
platform structs.  But if the consensus is it's cleaner to keep this
stuff in wflinfo I'm ok with that too.