piglit-dispatch: Code generation scripts.

This patch contains the code generation scripts that convert the files
gl.spec, gl.tm, and enumext.spec into C code, as well as the CMake
directives to run the scripts.

Code generation occurs in two phases: first the script
glapi/parse_glspec.py converts the .spec and .tm files into an
intermediate JSON format, which is stored in glapi/glapi.json.  Then,
the script tests/util/gen_dispatch.py converts the JSON file into two
files, tests/util/generated_dispatch.c and
tests/util/generated_dispatch.h.

There are two motivations for breaking code generation into two phases:
(1) there are other code generation tasks we may add in the future
(e.g. generating the tests/util/piglit-util-enum.c file), and it would
be nice not to have to rewrite any parsing code when we do so.  (2) if
the GL consortium ever decides to change the format of gl.spec, gl.tm,
and enumext.spec, then we only have to change parse_glspec.py.

These code generation scripts can be run by invoking "make
piglit_dispatch_gen" from the toplevel source directory.

v2: Add clarifying comments, remove a bogus "print" statement, and
raise an exception if an unrecognized multiplicity is encountered.
Also, handle "reference" multiplicity.

v3: Add APIENTRY to stub functions.  Rename "near" and "far" to avoid
problems on MSVC.  Get rid of "__" in function names.  Rename
initialize_dispatch_pointers => reset_dispatch_pointers.  Add
gl_10x_version parameter to get_core_proc().  Output generated code
relative to CMAKE_BINARY_DIR so that it won't pollute source
directories when building out of tree.  Add .gitignore so that
generated files are ignored when building in tree.  Add GL_VERSION_*
defines.
cmake: Move utility functions into piglit_util.cmake

Currently there is only one utility function, piglit_include_target_api.
However, subsequent commits will add several more.

I'm choosing to define all the utility functions in their own file,
piglit_util.cmake, in order to keep things organized and the top
CMakeLists uncluttered.

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
cmake: Define wrapper functions piglit_add_{executable,library}

For now, `piglit_add_executable` is a trivial wrapper around
`add_executable`.  Ditto for `piglit_add_library`.

A subsequent commit will leverage the wrappers to add to each object file
an explicit dependency on the header files generated by piglit_dispatch.

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
cmake: Replace calls to add_{executable,library} with wrappers

Replace
    add_executable -> piglit_add_executable
    add_library -> piglit_add_library

For now, each wrapper function trivially wraps the function it replaces,
and so this patch changes no behavior.

This commit was created using the command:

   sed -i -e "s/add_executable/piglit_add_executable/" -e "s/add_library/piglit_add_library/" $(find src/ tests/ -name "*CMakeLists*")

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
cmake: Make each *.o depend on generated piglit_dispatch headers

Alter the wrapper functions `piglit_add_executable` and
`piglit_add_library` to add to each object file a dependency on
piglit_dispatch's generated files. This requires that a top-level custom
target be created, `piglit_dispatch_gen`, to track that dependency.

The result is that updating any files in `piglit_dispatch_gen_inputs` (for
example, gl_API.xml) triggers a recompile of all objects.

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
piglit-dispatch: Remaining infrastructure.

Previous patches introduced code generation for the auto-generated
portions of the piglit-dispatch mechanism.  This patch supplies the
remaining hand-written code, which includes:

- Code to initialize piglit-dispatch.

- The actions to be taken when looking up a function, when function
  lookup fails, or when a function is unsupported.

- Code to determine whether piglit-dispatch has been initialized,
  which GL version is supported, and whether a given extension is
  supported.

- Code to look up a function using a name supplied at run-time.

- Definitions of basic GL types.

v2: Make "inline" work in MSVC.  Only try to include "glxew.h" on
Linux.  Fix MSVC definition of int8_t.  Add #include
"piglit-dispatch.h" to piglit-dispatch.c for clarity.  Get rid of "__"
in function names.  Only call reset_dispatch_pointers() if necessary.
Use "\param" in comments.  Define APIENTRY/GLAPIENTRY properly on
Windows.  Implement get_core_proc_address() and get_ext_proc_address()
properly for Windows.
piglit-dispatch: Switch to using piglit-dispatch instead of GLEW.

Previous patches set up the piglit-dispatch infrastructure but did not
use it.  This patch enables piglit-dispatch and uses it instead of
GLEW.

- No piglit regressions on Intel SandyBridge (Linux) or the nVidia
  binary blob for Linux.

- One regression on Mac OSX: after this patch,
  shaders/gpu_shader4_attribs incorrectly skips.  This happens because
  the functions tested by shaders/gpu_shader4_attribs are defined in
  both EXT_gpu_shader4 and NV_vertex_program4 extensions.
  Piglit-dispatch is not yet capable of understanding that a function
  might be defined with the same name in multiple extension specs
  (because it is based on the gl.spec file from www.opengl.org, which
  fails to encode this information).  I plan to address this in a
  future patch.

- Spot checked on Microsoft Windows.

v2: Remove redundant includes of GL headers.
piglit-dispatch: Remove GLEW.

This patch removes the files glew.c and glew.h, which are no longer
used.  The "piglit-dispatch" mechanism is used instead.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Remove GLEW workarounds.

This patch removes workarounds that were in place to compensate for
bugs in GLEW.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
glean: use piglit_get_proc_address().

Previously glean got the address of GL functions by directly calling
an OS-specific function (e.g. glXGetProcAddressARB(), dlsym(), or
wglGetProcAddress()).  This patch changes it to use
piglit_get_proc_address(), which uses piglit-dispatch.  This will help
pave the way for adapting glean to test using GLES and
forward-compatible contexts.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>

v2: Changed the return type of glean's getProcAddress to "void
(APIENTRY *)()" so that no type casting is necessary on Windows.
Get rid of NVX stuff