Avoid full metrics computation with Update:FitCursor
The handling of Update::FitCursor traditionnally recomputes all
metrics once or twice. Now that updateMetrics(false) ensures that all
paragraphs that require it have a metrics, we might as well use that.
Take this occasion to move handling of Update::SinglePar earlier,
before the check for Update::ForceDraw.
Set buffer when creating a MathData from parts of another one
This is triggered by selecting part of an equation under Xcb platform
(x11). Indeed, the current selection has to be sent to the X11 server
and BufferView::requestSelection() is called. Eventually
cap::grabSelection() is the function that creates this partial
MathData object.
Set buffer_ correctly when inseting a math macro over a selection
The code that handles this special macro insertion (in
Cursor::mathMacroClose())) is very weird: it inserts the contents of
the macro _after_ the macro and later, since the macro is 'greedy', it
will eat this contents and put it in its first macro cell.
Does it make sense to you? It does not ake sense to me either. Anyway,
this is the point where one should make sure that the buffer is set.
When debug (-g) is enabled (default when compiling a development
version), the existing -O optimization level is not correct, since
many variables are optimized out when debugging.
Use -Og instead, and condition not on compiling a development version,
but on --enable-debug. This is the same by default, but it more
precise in our case.
