tests/drmsl: Extract tests out of xf86drmSL.c

v2: merge tests creation and xf86drmSL cleanup
    rename tests/drmsltest -> tests/drmsl
    move the test out of libudev test block
v3: run test even on noudev builds

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>
Acked-by: Emil Velikov <emil.l.velikov@gmail.com>
diff --git a/.gitignore b/.gitignore
index 06cc928..cb7128d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -74,6 +74,7 @@
 via.kld
 tests/auth
 tests/dristat
+tests/drmsl
 tests/drmstat
 tests/getclient
 tests/getstats