egl: add EGL_platform_device support

egl: add EGL_platform_device support

This new 'platform' is added by default with no guards.

It is effectively a copy of the surfaceless one, with updated function
names and brand new probe function.

Due to the reuse, some of the ifdef HAVE_SURFACELESS_PLATFORM guards
have been dropped.

A worthy mention are the changes in _egFindDisplay, since the original
and dup'd fd are required, we make use of the plat_opt argument.

Note that no hacks for eglGetDisplay are added - the API works only with
the eglGetPlatformDisplay* API.

v2:
 - s/_eglCompareDeviceDisplay/_eglSameDeviceDisplay/ (Eric)
 - let ^^ return bool (Eric)
 - fixup meson build, move files() further up (Eric)
 - copy from plat. surfaceless w/o the visual cleanups
 - close and free when destroying the dpy
 - sprinkle a few _eglDeviceSupports
 - split fd handling into separate function
 - use directly the render node if no FD is given (Mathias)

v3:
 - s/dpy/disp/g
 - drop swap_buffers* callbacks
 - drop loader_set_logger()
 - drop local define
 - re-introduce _eglGetDRMDeviceRenderNode()
 - EGL_WARN on ForceSoftware with HW device - continue using the HW device
 - bail out for "EGL_MESA_device_software" until it's fixed
 - wire-up the Android build

v4:
 - use new style _eglFindDisplay()
 - split hw vs sw code paths
 - don't close the internal fd (already handled in FiniDisplay())
 - make swrast work (bit hacky bit will do for now)
 - Android for real, drop autotools
 - Correct HW + LIBGL_ALWAYS_SOFTWARE check
 - use the dri2_create_drawable() helper

v5:
 - enhance comment around fd checks (Mathias)
 - rebase for dri2_init_surface() changes

Cc: Mathias Fröhlich <Mathias.Froehlich@gmx.net>
Acked-by: Marek Olšák <marek.olsak@amd.com> (v4)
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>