xwayland: Check status in GBM pixmap creation

The current code in `xwl_glamor_gbm_create_pixmap_for_bo()` may fail in
several cases that are not checked for:

 - `eglCreateImageKHR()` may have failed to create the image,
 - `glEGLImageTargetTexture2DOES()` may fail and set an error,
 - `glamor_set_pixmap_texture()` may fail for very large pixmaps
    because the corresponding FBO could not be created.

Trying to upload content to a pixmap with no texture will crash Mesa,
glamor and Xwayland, e.g.:

  XXX fail to create fbo.
  (EE)
  (EE) Backtrace:
  (EE) 0: Xwayland (OsSigHandler+0x29)
  (EE) 1: libpthread.so.0 (funlockfile+0x50)
  (EE) 2: libc.so.6 (__memmove_avx_unaligned_erms+0x215)
  (EE) 3: dri/i965_dri.so (_mesa_format_convert+0xab3)
  (EE) 4: dri/i965_dri.so (_mesa_texstore+0x205)
  (EE) 5: dri/i965_dri.so (store_texsubimage+0x28c)
  (EE) 6: dri/i965_dri.so (intel_upload_tex+0x13b)
  (EE) 7: dri/i965_dri.so (texture_sub_image+0x134)
  (EE) 8: dri/i965_dri.so (texsubimage_err+0x150)
  (EE) 9: dri/i965_dri.so (_mesa_TexSubImage2D+0x48)
  (EE) 10: Xwayland (glamor_upload_boxes+0x246)
  (EE) 11: Xwayland (glamor_copy+0x4d1)
  (EE) 12: Xwayland (miCopyRegion+0x96)
  (EE) 13: Xwayland (miDoCopy+0x43c)
  (EE) 14: Xwayland (glamor_copy_area+0x24)
  (EE) 15: Xwayland (damageCopyArea+0xba)
  (EE) 16: Xwayland (compCopyWindow+0x31c)
  (EE) 17: Xwayland (damageCopyWindow+0xd3)
  (EE) 18: Xwayland (miResizeWindow+0x7b7)
  (EE) 19: Xwayland (compResizeWindow+0x3a)
  (EE) 20: Xwayland (ConfigureWindow+0xa96)
  (EE) 21: Xwayland (ProcConfigureWindow+0x7d)
  (EE) 22: Xwayland (Dispatch+0x320)
  (EE) 23: Xwayland (dix_main+0x366)
  (EE) 24: libc.so.6 (__libc_start_main+0xf3)
  (EE) 25: Xwayland (_start+0x2e)
  (EE)
  Fatal server error:
  (EE) Caught signal 11 (Segmentation fault). Server aborting
  (EE)

Check for the possible cases of failure above and fallback to the
regular glamor pixmap creation when an error is detected.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Closes: https://gitlab.freedesktop.org/xorg/xserver/issues/661
(cherry picked from commit fc6380a1)