SystemInfo: Add active GPU backend.

For debugging it is useful to known the active GPU backend. Although
it could be determined from looking at the extensions, this is easier
to understand when not activly working in this area.

release/scripts/modules/sys_info.py

@@ -184,6 +184,7 @@ def write_sysinfo(filepath):
                 output.write("vendor:\t\t%r\n" % gpu.platform.vendor_get())
                 output.write("version:\t%r\n" % gpu.platform.version_get())
                 output.write("device type:\t%r\n" % gpu.platform.device_type_get())
+                output.write("backend type:\t%r\n" % gpu.platform.backend_type_get())
                 output.write("extensions:\n")
 
                 glext = sorted(gpu.capabilities.extensions_get())