vo_opengl: expose performance timers as properties

This is plumbed through a new VOCTRL, VOCTRL_PERFORMANCE_DATA, and
exposed as properties render-time-last, render-time-avg etc.

All of these numbers are in microseconds, which gives a good precision
range when just outputting them via show-text. (Lua scripts can
obviously still do their own formatting etc.)

Signed-off-by: wm4 <wm4@nowhere>

DOCS/man/input.rst

@@ -894,6 +894,30 @@ Property list
     .. note:: This is only an estimate. (It's computed from two unreliable
               quantities: fps and possibly rounded timestamps.)
 
+``render-time-last``
+    Time needed to render the last frame in microseconds. Not implemented by
+    all VOs.
+
+``render-time-avg``
+    Average of ``render-time-last`` over the last few frames. (The exact
+    averaging time is variable, but it should generally be a few seconds)
+
+``render-time-peak``
+    Peak (maximum) of ``render-time-last`` over the last few frames.
+
+``present-time-last``, ``present-time-avg``, ``present-time-peak``
+    Analogous to ``render-time-last`` etc. but measures the time needed to
+    draw a rendered frame to the screen. Not implemented by all VOs.
+
+    (This is separate from ``render-time-last`` because VOs may interpolate,
+    deinterlace or otherwise mix multiple source frames into a single output
+    frame)
+
+``upload-time-last``, ``upload-time-avg``, ``upload-time-peak``
+    Analogous to ``render-time-last`` etc. but measures the time needed to
+    upload a frame from system memory to a GPU texture. Not implemented by all
+    VOs.
+
 ``path``
     Full path of the currently played file. Usually this is exactly the same
     string you pass on the mpv command line or the ``loadfile`` command, even