4506f614cb fixed parsing of textual IR to
reject `ptr*`, but broke the auto-conversion of `i32**` to `ptr` with
`--force-opaque-pointers`.
Get that working again by refactoring LLParser::parseType to only send
`ptr`-spelled pointers into the type suffix logic when it's the return
of a function type. This also rejects `ptr addrspace(3) addrspace(2)`,
which 1e6303e60c invadvertently started
accepting. Just the default top-level error message for the
double-addrspace since I had trouble thinking of something nice;
probably it's fine as is (it doesn't look valid the way that `ptr*`
does).
Differential Revision: https://reviews.llvm.org/D105146
Duncan P. N. Exon Smith