Fix build warnings on some platforms

Fix build warnings on some platforms

Use an explicit cast from size_t to int to avoid errors like the following:
glslang\glslang\MachineIndependent\preprocessor\Pp.cpp(1053) : error C2220: warning treated as error - no 'object' file generated
glslang\glslang\MachineIndependent\preprocessor\Pp.cpp(1053) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data

affects Pp.cpp, hlslParseHelper.cpp.

Initialize local variable to get rid of warningsa about potentially
uninitialized variables:
glslang\hlsl\hlslparsehelper.cpp(3667) : error C2220: warning treated as error - no 'object' file generated
glslang\hlsl\hlslparsehelper.cpp(3667) : warning C4701: potentially uninitialized local variable 'builtIn' used

affects hlslParseHelper.cpp