Renames:
----------------------------------------
obs_source_add_child
obs_source_remove_child
obs_source_enum_sources
obs_source_enum_tree
obs_source_info::enum_sources

To:
----------------------------------------
obs_source_add_active_child
obs_source_remove_active_child
obs_source_enum_active_sources
obs_source_enum_active_tree
obs_source_info::enum_active_sources

These functions/callbacks had misleading names: they originally implied
any child sources, when they actually meant active child sources that
are being used to render video or audio.  It's important that the
function names represent their actual purpose.

Prunes code used to workaround libobs "user sources" (such as
sourceSceneRefs) and instead simply holds its own references and saves
sources it chooses with obs_save_sources_filtered.

(Note: This commit breaks UI compilation.  Skip if bisecting)

Ensures that a reference is kept until the signals associated with that
reference are disconnected.

(Note: This commit breaks UI compilation.  Skip if bisecting)

Adds a means of saving specific sources that the front-end chooses,
rather than being forced to use the now-removed "user list".

(Note: This commit breaks UI compilation.  Skip if bisecting)

API Removed:
------------------------
obs_add_source

API Changed:
------------------------
obs_source_remove: Now just marks/signals a source for removal

The concept of "user sources" is flawed: it was something that the
front-end was forced to deal with if it wanted to automate source
saving/loading, and often it had to code around it.  That's not how
saving/loading should work, a front-end should be allowed to manage
lists of sources in the way it explicitly chooses, and it should be able
to choose which sources it wants to save/load.

These signals are meant to replace the add/remove signals.

These functions created stack variables but never actually initialized
them.  If the calldata variable is invalid, the return values will be
the uninitialized stack value.

The name was inconsistent with the darray_swap function that it's a
macro for.

This function was removed even though the browser plugin was using this
function on mac, so this is being put back in temporarily while the
browser plugin is modified to remove this function.

Some games don't catch GL errors via glGetError, so there's a
possibility that an error will pass through to the capture calls,
causing a false failure.

The most simple solution is to just clear the error flag on each capture
call.

With certain devices (AVerMedia C985 and LGP), audio timestamps are
bad, and a 50ms threshold of audio data "smoothing" (making consecutive
audio packets seamless with one another) isn't enough to handle bad
consecutive timestamp values.  After testing, 70ms sufficiently solves
the issue.

This will probably go away once proper file name formatting is
implemented (https://obsproject.com/mantis/view.php?id=361)

Given a config file with some value "foo=\\n" querying the value of foo
would return {'\\', '\n', 0}, instead of {'\\', 'n', 0}

This enables e.g. the HLS muxer to output all files in the same directory, with
appropriate names

This shouldn't happen anymore because crop was fixed, but if a filter
returns 0x0 size and is invalid it shouldn't stop the filter chain.
Instead, it should just be skipped.

To first render the filter, the width/height values must be set, but
currently they're only set in the render function, which means that the
crop filter can never be rendered when the program first starts up.
This would cause the filter to fail to render at all under those
circumstances.

This patch moves the calculations from render to tick to ensure that
they're always called and the values are always set.

The virtual address table values for Reset/ResetEx can sometimes point
to functions that are in libraries outside of D3D8.dll and D3D9.dll, and
will cause a crash if used.  Instead, just hook Reset/ResetEx when one
of the Present* functions are called.

SIGTRAP is the correct value to use to specify a breakpoint.

Fixes warning (clang):

variable 'added_packet' is used uninitialized whenever 'if' condition is
false [-Wsometimes-uninitialized]

Since the RTMP_Close was moved to the send thread (where it should have
been) the stop thread now has no real purpose.

This forces proper crash handling to generate a stack trace.