Change graphics subsystem to 4x4 matrices

4x4 matrices aren't as optimal, but are much more sensible to handle
when you want to do more advanced stuff like scaling, skewing, or
inversion.
Merge pull request #113 from jp9000/matrix-update

Change graphics subsystem to 4x4 matrices
Fix bug with creating immediate vertex buffers

Check to make sure graphics subsystem pointer isn't null before
derefrencing, and fix bugs when creating vertex buffers from
immediate-style helpers
d3d11: Fix bug creating static vertex buffers

The vertex data wasn't getting properly freed, it was actually setting
the parameter itself to null for some reason.
Allow signal callback deletion while signalling

I encountered a situation where I wanted to delete a callback for a
signal while inside of that signal.  However it would hard lock, and
even after that, it would mess up the loop for the callback list.

So, change the mutex of the individual signals to a recursive-style
mutex, and then if a callback of a signal is deleted while currently in
that signal, just mark it for deletion, which will happen after the
signal is complete.
Fix null pointer dereference in text lookup

Fix potential null pointer dereference for when splitting a node.
win-capture: Fix bug calculating cursor position

Cursor position calculation was not taking in to account the window
client coordinates relative to the screen.
libobs:  Add 'solid' effect for basic primitives
libobs:  Add helper functions for math data
Add solid_effect variable to obs_core_video
Make a minor OCD tweak to align parameters
Scenes:  Implement more item positioning features

There are a ridiculous number of features related to scaling and
positioning due to requests by a number of people who complained that
they hated the way that OBS1 would always resize their sources when the
source's base size changed.  There were also people who wanted more
control for how the resizing was handled, or the ability to completely
prevent resizing entirely if desired.  So I made it so that you can
optionally use a 'bounds' system, which allows you to specify different
styles of controlling resizing.

If disabled, the source will always automatically resize and only the
base scale is applied.  If enabled, you have a variety of different ways
to limit/control how it can resize within the bounds, or make it so it
can't resize at all.  You can also control alignment within that
bounding box, so you can make it so that a source always aligns to a
side or corner of the box.

I also added an alignment value which changes how the source is oriented
relative to the position of the scene item.  For example, setting
bottom-right alignment will make it so that the position of the item is
the bottom right corner of the source.  When the source resizies, it
will resize leftward and upward in that case, which solves the problem
of how a source resizes relative to a desired position.
UI:  Add scene editing

So, scene editing was interesting (and by interesting I mean
excruciating).  I almost implemented 'manipulator' visuals (ala 3dsmax
for example), and used 3 modes for controlling position/rotation/size,
but in a 2D editing, it felt clunky, so I defaulted back to simply
click-and-drag for movement, and then took a similar though slightly
different looking approach for handling scaling and reszing.

I also added a number of menu item helpers related to positioning,
scaling, rotating, flipping, and resetting the transform back to
default.

There is also a new 'transform' dialog (accessible via menu) which will
allow you to manually edit every single transform variable of a scene
item directly if desired.

If a scene item does not have bounds active, pulling on the sides of a
source will cause it to resize it via base scale rather than by the
bounding box system (if the source resizes that scale will apply).  If
bounds are active, it will modify the bounding box only instead.

How a source scales when a bounding box is active depends on the type of
bounds being used.  You can set it to scale to the inner bounds, the
outer bounds, scale to bounds width only, scale to bounds height only,
and a setting to stretch to bounds (which forces a source to always draw
at the bounding box size rather than be affected by its internal size).
You can also set it to be used as a 'maximum' size, so that the source
doesn't necessarily get scaled unless it extends beyond the bounds.

Like in OBS1, objects will snap to the edges unless the control key is
pressed.  However, this will now happen even if the object is rotated or
oriented in any strange way.  Snapping will also occur when stretching
or changing the bounding box size.
UI:  Add padding to scene edges for editing

Add a 10 pixel padding to the sides and remove viewport cutting to
ensure that the editing rectangles are visible even when in the upper
corners.

Also, add a black background for the actual 'scene' in the preview
window so that the scene boundries are actually visible in relation to
the rest of the preview space.
Merge pull request #114 from jp9000/scene-editing

Scene editing
Return index of added property list entry
Allow property list entries to be disabled

This allows, for example, disconnected devices for dshow/avcapture to
be listed (and to stay selected in the user config) while making them
unavailable for selection in new sources
Make properties-view respect disabled list entries
Add include for ptrdiff_t
Unify obs_data_get* and obs_data_item_get* functions handling