llvm-svn: 171898

and adds a new file ReaderWriterYAML.cpp that uses YAML I/O.

Lots of tweaks to test suite for slightly different YAML encoding.

llvm-svn: 171592

recursive descent functions into one table driven parser.  Add proper
error recovery and reporting.  Add lots of test cases with semantics errors
and verify error messages.

llvm-svn: 156136