Add optional GL_KHR_debug support

Not much thought went into that one...

HLE/Sockets: Fixed the buffer offset in recvfrom.

Update appveyor.yml to use VS2015 CMake generator

Gamelist: supply default settings for QSettings config

services: Update some function tables

arm_dyncom_dec: Fix decoding of VMLS

Previously, all VMLS variants would misdecode as CDP
(which isn't necessarily wrong in itself, however
VMLS has it's own label of execution)

video_core: Make the renderer global a unique_ptr

HLE/Timers: Reset OneShot timers when they are acquired instead of when they're triggered

core: Use unique_ptr for holding the interpreter instances

Closes #1139

swrasterizer: Add missing override specifier

SVC: Fixed ArbitrateAddress to behave as it does on hardware.

dyncom: Handle modifying the APSR via an MRC instruction

This was verified with hwtests that i plan to upload later on.

svc: Remove superfluous printf argument

Add a return value in ForeachDirectoryEntry 

Closes #1277

dyncom: Minor changes

ForeachDirectoryEntry is changed by #1256 ,but return value at last line
was missing.

These instructions aren't capable of using the PC as a destination

VideoCore: Sync state after changing rasterizers

This fixes various bugs that appear in the HW rasterizer after switching
between it and the SW one during emulation.

LDRT/LDRBT/STRBT/STRT should simulate the load or store
as if the host CPU is in user mode.

STRT is also allowed to use the PC as an operand

svc: Fix compilation with LOG_TRACE enabled

OpenGL: Flip framebuffers during transfer rather than when rendering

GPU/PrimitiveAssembler: Fixed drawing triangle fans.

VideoCore: Unify interface to OpenGL and SW rasterizers

This removes explicit checks sprinkled all over the codebase to instead
just have the SW rasterizer expose an implementation with no-ops for
most operations.

dyncom: Miscellaneous minor changes