r19019: Add a parser for javascript literals. This is implemented for parsing JSON

r19019: Add a parser for javascript literals.  This is implemented for parsing JSON
strings, but is generally useful for creating ejs variables from object or
array literals, which aren't supported in the old version of ejs that we're
using.

This parser is implemented in C, but is callable from an ejs script via
literal_to_var().
(This used to be commit 82fdcd9339a8ffb1016b96c06f7d6580aa759174)