SQL JSON path enhanced numeric literals

Attached is a patch to add nondecimal integer literals and underscores 
in numeric literals to the SQL JSON path language.  This matches the 
recent additions to the core SQL syntax.  It follows ECMAScript in 
combination with the current SQL draft.

Internally, all the numeric literal parsing of jsonpath goes through 
numeric_in, which already supports all this, so this patch is just a bit 
of lexer work and some tests.