gdk: backport GdkProfiler

This is a backport of the GdkProfiler from master. It does not include the pixel bandwidth numbers that come from gdkdrawcontext.c since there does not seem to be an analog in 3.x.

Additionally, this implements the recent changes for SYsprof's D-Bus profiler API which adds a Capabilities property and an options hash-table to the D-Bus interface for forward portability.

added 9. Initiative: Platform Profiling label

mentioned in issue Initiatives#10 (closed)

mentioned in commit dcdab5b8

merged