This needs some render testing, but is destined to be part of master.
This also leads to a variety of other simplifications.
- IO are global symbols, so only need one list of linkage nodes (deferred)
- no longer need parse-context-wide 'inEntryPoint' state, entry-point is localized
- several parts of splitting/flattening are now localized
If some DCE is performed such as removing dead functions, then even
if we are NOT stripping debug info, we still must remove the debug
opcodes that refer to the now-dead IDs.
Also, this adds a small change to perform no ID remapping if none
is requested, making spirv-remap properly be a no-op if no options
are given.
Takes some pressure off of issue #304.
Structures don't inherit locations and then explicitly decorate
members with them, so removed this reason to have another instance
of a structure type.
