We're only using the HLSL code in Windows so
it's not necessary to compile and distribute it on other platforms.

This adds a defined ANGLE_ENABLE_HLSL that can be checked in files that
are used by non-HLSL code as well. Mostly the HLSL code is just not
include by the build system.

Details of the space savings (heavily truncated)

Total change: -165717 bytes
===========================
 -606 - Source: angle/src/common/utilities.cpp
 -627 - Source: angle/src/compiler/translator/FlagStd140Structs.cpp
 -695 - Source: /usr/include/c++/4.8/bits/stl_algo.h
 -710 - Source: angle/src/compiler/translator/TranslatorHLSL.cpp
 -713 - Source: angle/src/compiler/translator/IntermNode.h
 -863 - Source: /usr/include/c++/4.8/bits/stl_map.h
 -935 - Source: angle/src/compiler/translator/blocklayout.cpp
 -1515 - Source: angle/src/compiler/translator/BuiltInFunctionEmulator.cpp
 -1655 - Source: angle/src/compiler/translator/UnfoldShortCircuit.cpp
 -2375 - Source: /usr/include/c++/4.8/bits/vector.tcc
 -3135 - Source: angle/src/compiler/translator/RewriteElseBlocks.cpp
 -4656 - Source: angle/src/compiler/translator/UtilsHLSL.cpp
 -5265 - Source: angle/src/compiler/translator/BuiltInFunctionEmulatorHLSL.cpp
 -6505 - Source: /usr/include/c++/4.8/bits/stl_tree.h
 -11480 - Source: angle/src/compiler/translator/UniformHLSL.cpp
 -13580 - Source: angle/src/compiler/translator/StructureHLSL.cpp
 -18964 - Source: ??
    (constant strings and a few vtbls)
 -89332 - Source: angle/src/compiler/translator/OutputHLSL.cpp

Change-Id: I23ccc98abd0a21f847dd34f9482800b3ba679d56
Reviewed-on: https://chromium-review.googlesource.com/251528Tested-by: bratell at Opera <bratell@opera.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>