Currently the utils/ folder uses both spvutils:: and spvtools::utils.
This CL changes the namespace to consistenly be spvtools::utils to match
the rest of the codebase.
Now we have public headers arranged as follows:
$SPIRV_TOOLS_ROOT/include/spirv-tools/libspirv.h
$SPIRV_TOOLS_ROOT/include/spirv/spirv.h
$SPIRV_TOOLS_ROOT/include/spirv/GLSL.std.450.h
$SPIRV_TOOLS_ROOT/include/spirv/OpenCL.std.h
A project should use -I$SPIRV_TOOLS_ROOT/include
and then #include "spirv-tools/libspirv.h"
The headers from the SPIR-V Registry can be accessed as "spirv/spirv."
for example.
The install target should also install the headers from the SPIR-V
Registry. The libspirv.h header is broken otherwise.
The SPIRV-Tools library depends on the headers from the SPIR-V Registry.
The util/bitutils.h and util/hex_float.h are pulled into the internal
source tree. Those are not part of the public API to SPIRV-Tools.
