[SemaObjC] Be more strict while parsing type arguments and protocols

Fix a crash-on-invalid.

When parsing type arguments and protocols,
parseObjCTypeArgsOrProtocolQualifiers() calls ParseTypeName(), which tries to
find matching tokens for '[', '(', etc whenever they appear among potential
type names. If unmatched, ParseTypeName() yields a tok::eof token stream. This
leads to crashes since the parsing at this point is not expected to go beyond
the param list closing '>'.

Fix that by properly handling tok::eof in
parseObjCTypeArgsOrProtocolQualifiers() callers.

Differential Revision: https://reviews.llvm.org/D23852

rdar://problem/25063557

llvm-svn: 281383