For fulfilling this purpose, the |opcode| field in the
|spv_parsed_instruction_t| struct is changed to of type uint16_t.
Also add functions to query the information of a given SPIR-V
target environment.
This patch uses a Python script to parse the JSON grammar file to
generate the opcode table and operand kind tables.
Now we don't need to do the post-processing (from OperandClass
to spv_operand_type_t) and copying of the opcode info table is
not required anymore!
