Reason Printer: Add more location source maps at print time.
Reason Printer: Add more location source maps at print time.

Summary: This is required in order to enable intelligent printing of
trailing commas, but probably improves some other printings too. The
SourceMap was just lost at some point on these AST structures.

Test Plan:

Reviewers:

CC:

let-def/reason,cristianoc/reason,facebook/reason,cristianoc/reason,cristianoc/reason,facebook/reason,chenglou/reason,facebook/reason,chenglou/reason,chenglou/reason,let-def/reason,let-def/reason