Added syntax->datum+stx-hash, tested to return same datum as syntax->datum on ragg syntax objects.
AST SrcLoc format & parameter, first test in source position and error messages, option for srcloc-less AST for parser tests
get-structured-python shucks SrcPos and reports error position as the closest known enclosing SrcPos
Some statements have source location; initial tests in source locations
Source position on most statements & tested
All statements have SrcLoc from parser.
Merge branch 'master' of https://github.com/brownplt/lambda-py
Temp disabling srcloc on arguments to work with changes in get-structured-python