Clean up SPIR-V support code in framework

Clean up SPIR-V support code in framework

 * Return result codes instead of exceptions when GLSL compilation or
assembling fails. Reserve exceptions for unexpected errors.

 * Move vk::disassembleSpirV() to vkSpirVAsm.cpp/hpp.

 * Use deUint32 vectors/pointers for passing around SPIR-V binary data.
Consolidate endianness handling to vkPrograms.cpp.

 * Log disassembled GLSL shaders as <SpirVAssemblySource>.

 * Enable validation for glslang-generated SPIR-V binaries. Requires
updating both glslang and spirv-tools.

 * Clean up vk::SpirVAsmSource and vk::SpirVProgramInfo.

 * Clean up some potential resource leaks in spirv-tools integration.

 * Add --validate-spv option to vk-build-programs.

Change-Id: I0d5683c83c16b3e6d794e284c17ed65ea9541a35