Use standard .gitignore file and layout

Reusing xorg code saves maintenance in the long term.

Now that m4/.gitignore is removed, the -I m4 ${ACLOCAL_FLAGS}
must be removed to avoid build breakage as m4 is generated and not
part of the git source.

Acked-by: Cyril Brulebois <kibi@debian.org>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Gaetan Nadon <memsize@videotron.ca>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

tests/.gitignore

@@ -0,0 +1,51 @@
+gem_bad_address
+gem_bad_batch
+gem_bad_blit
+gem_bad_length
+gem_basic
+gem_double_irq_loop
+gem_dummy_reloc_loop
+gem_exec_bad_domains
+gem_exec_blt
+gem_exec_faulting_reloc
+gem_exec_nop
+gem_fenced_exec_thrash
+gem_fence_thrash
+gem_flink
+gem_gtt_speed
+gem_gtt_speed
+gem_hang
+gem_hangcheck_forcewake
+gem_largeobject
+gem_linear_blits
+gem_mmap
+gem_mmap_gtt
+gem_partial_pwrite_pread
+gem_pipe_control_store_loop
+gem_pread_after_blit
+gem_pwrite
+gem_readwrite
+gem_reloc_vs_gpu
+gem_ringfill
+gem_ring_sync_loop
+gem_storedw_batches_loop
+gem_storedw_loop_blt
+gem_storedw_loop_bsd
+gem_storedw_loop_render
+gem_stress
+gem_tiled_blits
+gem_tiled_fence_blits
+gem_tiled_pread
+gem_tiled_pread_pwrite
+gem_unref_active_buffers
+gem_vmap_blits
+gen3_mixed_blits
+gen3_render_linear_blits
+gen3_render_mixed_blits
+gen3_render_tiledx_blits
+gen3_render_tiledy_blits
+getclient
+getstats
+getversion
+testdisplay
+# Please keep sorted alphabetically