Reduces required scrolling when lots of new audio sources are added
(e.g. aux devices being enabled in the same dialog) when the dialog
was opened with just a few audio sources being present. Unfortunately,
the "restart required" warning is pushed all the way to the bottom
even if the source list is empty

The screen index returned from XDefaultScreen is 0-based, and we were
decrementing it before the check to see if it had reached 0 rather than
after, so in the default_screen function it would always end up getting
either the wrong screen or no screen.

When xcb_query_pointer and xcb_query_pointer_reply was called with no
valid screen, it would fail with an error, thus making it so that the
mouse buttons could not be properly captured as hotkeys.

This probably fixes the crash from "libobs: Check effect mutex exists
before destroying it" (c2c47b11)

This reverts commit c2c47b11.

Fixes a crash if graphics system didn't finish intializing.

This should allow entering alt + numpad N (N > 0) on windows since there
doesn't seem to be a way to completely ignore input events generated
from "alt codes"

This is just for visuals, no functionality change

Removed code where if a PTS diff was greater than a certain
threshold it was forced to the previous PTS diff.  This breaks
variable length frame media like GIF.

This prevents odd behavior with Qt5.4 turning the rounded buttons
into square push buttons.

UI supplied per scene hotkey to allow switching between scenes; this
has to be done in the UI since it's up to the application to define
what exactly "changing/selecting a scene" means (changing the output
of channel 0 may not be enough for other applications)

OBSHotkeyEdit is similar to QKeySequenceEdit, except less terribad on OSX, while
OBSHotkeyWidget provides a container that automagically encapsulates multiple
bindings per hotkey

OBSHotkeyLabel in combination with OBSHotkeyWidget provides mechanisms for
dealing with hotkey pairs (see upcoming usage in window-basic-settings.cpp)

Found by clang-3.7 (trunk 236075) via -Wpointer-bool-conversion:

warning: address of array 'rs->output_buffer' will always evaluate
to 'true'

When a reconnect is occurring, the user doesn't really know that the
program is waiting to reconnect to the server or not, nor does the user
know how many seconds are remaining until that next attempt.  This will
show the reconnect timeout countdown as it's occurring.

Implements exponential backoff for consecutive reconnects, which is
useful to prevent too many connections from trying to reconnect back to
a service at once over a short period of time in the case of potential
service downtime.  Exponential backoff causes each subsequent reconnect
attempt to double its timeout duration.

This optionally allows the front-end to know what the current timeout
value in seconds is set to for the reconnection without having to call
an extra API function to find that out.

QToolTip's (background) color(s) would not apply on windows, work-around
taken from https://forum.qt.io/topic/24023/