CMake: Updated to better organize folders and options.

Use strtoll, as stoll is unavailable on Android.

This adds solution folders that properly group gtest/glslang/hlsl.
This also marks gtest options as advanced so they don't show up
in cmake-gui by default.

Avoid printing to stdout directly in library functions.

README: Explain test organization and deduplication.

Previously GlslangToSpv() reported missing/TBD functionalities
by directly writing to stdout using printf. That could cause
problems to callers of GlslangToSpv(). This patch cleans up
the error reporting logic in GlslangToSpv(), TGlslangToSpvTraverser,
and spv::Builder a little bit to use ostringstream.

Also fixed the usage of GlslangToSpv() in GTest fixtures to
capture warnings/errors reported when translating AST to SPIR-V.

Add new built-in variables and functions to the parser (SPIR-V tokens are missing).

CMake: Remove duplicated cmake_minimum_required() calls.

This should be the last commit in this sequence to form the base of the work
in pull request #222.

This partly overlaps pull request #222, we have divided the work on this one.

This hopefully prevents obsucuring actual changes in a future commit.

Also, adds a script to update the grammar.

Remove the obselete and incorrect LinusDoAll.bash.

CMake: Bump minimum required CMake version to 2.8.12.

CMake 2.8.12 added support for target_include_directories(), among
other features, and we would like to use it.

Testing: Add configuration for Travis to test on Linux and Mac OS X.

Note this requires test-based piecing together of the preamble string,
so it changed to being a std::string to make it easier to do.

This closes issue #254.

This is a replacement commit for pull request #238.

This is a design change, followed by implementation change that
A) fixes the changes caused by the design change, and
B) fixes some cases that were originally incorrect.

The design change is to not give built-in functions default precision qualification.
This is to allow the rule that the precision of some built-in functions adopt their
precision qualification from the calling arguments.  This is A above.

A consequence of this design change is that all built-ins that are supposed to have
an explicit precision qualifier must now be declared that way.  So, a lot more
built-in declarations now have precision qualifiers, just to keep things the same.
This is B above.

Remove unused files SetupLinux.sh and index.php.

Full stack: Implement the extension GL_ARB_gpu_shader_int64