Also removed un-necessary heap-allocation of spv_named_id_table.
This removed the necessity to expose a function to create/destroy it
and simplified the interface.
You can't use names from 3.12 Image Channel Order and
3.13 Image Channel Data Type since in the intstruction grammar,
they are only used as return values, but never named arguments
to instructions.
You can't use a named enumerant if it's only meaningful
in an operand supplied as an ID to a target instruction.
The place where you'd use the name is something like an
OpConstant, but there's not enough context to bring those
names into scope, unless you're willing to tolerate
potential collisions.
Occurs for the names in:
- 3.25 Memory Semantics
- 3.27 Scope ID
- 3.29 Kernel Enqueue Flags
- 3.30 Kernel Profiling Info
