libobs: Add volume meter object

This adds a volume meter object to libobs that can be used by the GUI
or plugins to convert the raw audio level data from sources to values
that can easily be used to display the audio data.
The volume meter object will use the same mapping functions as the
fader object to map dB levels to a scale.
libobs: Add IEC 60-268-18 compliant fader type

This adds a new fader type that implements a position/dB mapping
as specified in IEC 60-268-18.
libobs: Add Logarithmic fader type

This adds the conversion function used by the old obs based on a
logarithmic scale.
obs/libobs: Use new volume meter api

This replaces the old code for the audio meter that was using
calculations in two different places with the new audio meter api.
The source signal will now emit simple levels instead of dB values,
in order to avoid dB conversion and calculation in the source.
The GUI on the other hand now expects simple position values from
the volume meter api with no knowledge about dB calculus either.
That way all code that handles those conversions is in one place,
with the option to easily add new mappings that can be used
everywhere.
Merge pull request #306 from fryshorts/volume-meter-improvements

Volume meter improvements
libobs: Add flush to video pipeline

On certain GPUs, if you don't flush and the window is minimized it can
endlessly accumulate memory due to what I'm assuming are driver design
flaws (though I can't know for sure).  The flush seems to prevent this
from happening, at least from my tests.  It would be nice if this
weren't necessary.
win-capture: Always set class/title/exe to null

When getting the class/title/exe of a particular window handle in the
build_window_strings function, always set the class/title/exe pointers
to null to prevent any potential references to invalid values if any of
them do not happen to be set for whatever reason.
win-capture: Add obfuscation functions

This adds obfuscation functions primarily for use with GetProcAddress.
This takes an obfuscated string and uses a simple integer key to
de-obfuscate it to the intended function name string, which is then
loaded dynamically using GetProcAddress.

This is typically only used with functions such as OpenProcess,
SetWindowsHookEx, and the like, which can often be misinterpreted the
wrong way by security programs if those strings are found within the
strings segment of a scanned executable.
win-capture: Obfuscate OpenProcess in win-helpers

OpenProcess can often be misinterpreted as invasive.  To avoid it, a
simple obfuscation workaround does the trick.
win-capture: Fix a bug with INCLUDE_MINIMIZED

This fixes a bug where if INCLUDE_MINIMIZED was set and the window size
was (0, 0), the window would still be excluded from the resulting list
that was created.
win-capture: Expose get_window_exe as extern

This allows get_window_exe to be used with other .c files in the module.
Add ipc-util static library for IPC functions

Originally I made the "win_pipe" stuff for named pipes on windows but it
was argued that it should be available to all modules and
programs/libraries that the modules might communicate with.

It cannot really be put in to libobs due to the fact that there would
hypothetically be things unrelated to libobs that might want to use it,
so I felt the best option was just to create a simple static library
specific for interprocess communication.

Non-windows versions of these functions are still yet to be implemented.
libobs: Fix conversion shader D3D display bug

Just for a quick background: D3D's fmod intrinsic is very imprecise.
Naturally floating points aren't precise at all, and when the numbers
you're dealing with become very large, it can often be off by 0.1 or
more.

However, apparently 0.1 isn't enough of an offset to ensure a proper
value when using the fmod intrinsic and then flooring the value.  0.2
seems to fix the issue and make the image display properly.
libobs-opengl: Don't display unimportant messages

The glDebugMessageCallback function will set a callback that will relay
all messages coming from the driver (on supported drivers at least).
For nvidia, sometimes there are a lot of irrelevant messages, which is
nice depending on the type of application you're writing.

I actually at first thought these messages were important, but it turns
out that they're almost always irrelevant and not actually warnings.
Most of the messages at a certain type/severity are mostly for debugging
purposes or minor hints about how to maximize performance, so
unfortunately there ends up being a lot of pointless spam in the debug
output.

The particular performance messages are related to optimizations you can
get via multithreading, and are optimizations you would expect for games
more than for this type of application.  They don't really apply for our
use cases most of the time.

High severity messages however are not omitted regardless of message
type.

These messages can be enabled again by simply defining the
SHOW_ALL_GL_MESSAGES macro.
libobs: Add obs_property_list_insert_* functions

These functions allow you to insert items at a specific index in a list
instead of being forced to always append to the end.
win-capture: Add hooking functions

These functions allow the safe hooking of windows functions,
specifically windows API functions that may or may not have built-in
machine code to help aid in reverse chain hooks.

If a new hook is applied to an existing forward hook, that hook will be
preserved to prevent that new hook's data from being removed
unintentionally.

Hopefully with all these precautions this will reduce the likelihood of
crashes and abnormal hook behavior, while allowing existing hooks to be
preserved, and allowing new hooks to be applied.
win-capture: Add hook helper functions for IPC

These inline functions simplify the process of using windows IPC
objects, such as mutexes and events.
win-capture: Add graphics-hook-info.h

This header contains global defines, structures, and helper inline
functions for the graphics hook that will be shared between game
capture, the hook, and the get-graphics-addrs helper application.
win-capture: Add d3d8 headers

These headers allow Direct3D 8 to be used.
win-capture: Add get-graphics-offsets helper

Before, game capture would find addresses to important graphics
functions by creating a graphics context for the desired API inside of
the hook, and then find the function addresses that way.

The big problem with that is that the context could often cause the
hooked application to crash, especially if another hook was active.

This bypasses that entire need by a simple console application that
creates the contexts, finds the hook address offsets and then returns
them via console output.