Jonas Ådahl authored May 15, 2018 and Georges Basile Stavracas Neto committed May 31, 2019

Add the ability to add tracing instrumentation to the code. When
enabled, trace entries will generate a file with timing information
that will be processable by sysprof for generating visualization of
traces over time.

While enabled by default at compile time, it is possible to disable the
expansion of the macros completely by passing --disable-tracing to
./configure.

Tracing is so far only actually done if actually enabled on explicitly
specified threads.

This will be used by Mutter passing the write end of a pipe, where the
read end is sent to Sysprof itself via the D-Bus method 'Capture()'.

By passing that, we have to detect EPIPE that is sent when Sysprof stops
recording. Fortunately, we already ignore the signal at meta_init(), so
no need to add a custom signal handler.

GNOME/mutter!197