TEMP/fix 64-bit flag

Master was updated with a new 64-bit build flag, but it didn't work
properly.
git: add install_log.txt to .gitignore
posix: ensure __POSIX__ define

To be used in later pieces of code that can be shared between OSX and Linux
(and possibly even others that comply).
pcsx2defs.h: use stdbool/bool instead of u8

Code line and duplication reduction.
pcsx2defs.h: don't define __fastcall on x64

It's not useful. POSIX systems always use the SysV ABI on x64, and Windows
systems use either the MS ABI (which also passes a lot of registers, so
bascically what fastcall did) or the "Vector Calling Convention" [1], which
needs to be explicitly enabled.

[1]:
http://blogs.msdn.com/b/vcblog/archive/2013/07/12/introducing-vector-calling-convention.aspx
64-bit: include __fastcall def in ScopedAlloc.h

I find it a bit strange that this is necessary, as far as I can see,
ScopedAlloc.h is included by Dependencies.h. Which in turn includes
Pcsx2Defs.h _before_ ScopedAlloc.h.
Remove redundant memzero_ptr. All compilers use SSE implementation anyway.
osx: use simple libc memcmp on OSX

It's plenty fast.
64-bit: AlignedMalloc header size = size_t != u32

u32 is size_t on 32-bits, but not on 64-bits. The proper type for a size
type like this is size_t anyway.
64-bit, osx: implement cross-plat __debugbreak()

__debugbreak is a MSVC instrinsic, which strangely enough is also
implemented in apple clang (and in vanilla clang, with -fms-extensions, but
this has its own problems). Not
in gcc as far as I know.

Luckily, there's a liberally licensed header file by Scott Tsai which takes
care of the cross platform (ARM/x86/x64) and cross-compiler issues.

https://github.com/scottt/debugbreak

debugbreak.h was taken from that 2-clause BSD-licensed project.

Other references:

Is there a portable equivalent to DebugBreak()/__debugbreak?
http://stackoverflow.com/questions/173618/is-there-a-portable-equivalent-to-debugbreak-debugbreak

__debugbreak() in apple clang but not vanilla, how to detect
http://stackoverflow.com/questions/25792878/debugbreak-in-apple-clang-but-not-vanilla-how-to-detect

The build error this patch solves (OSX/clang) is listed below. The reason it
happens is because on apple clang, __debugbreak is already declared.

[  1%] Building CXX object common/src/Utilities/CMakeFiles/Utilities.dir/AlignedMalloc.cpp.o
In file included from common/src/Utilities/AlignedMalloc.cpp:19:
In file included from common/src/Utilities/./PrecompiledHeader.h:21:
In file included from common/include/Utilities/Dependencies.h:193:
In file included from common/include/Pcsx2Defs.h:32:
common/include/intrin_x86.h:104:55: error: static declaration of '__debugbreak' follows non-static declaration
static __inline__ __attribute__((always_inline)) void __debugbreak(void)