Unable to make rule for literal backtick

[srgraham]

I get errors whenever I try to make any rule with a literal backtick. All of these throw:

backtick = "`"
backtick = '`'
backtick = "\x60"
backtick = '\x60'
backtick = "\u0060"
backtick = '\u0060'

All give this error and stack trace:

/Library/WebServer/htdocs/github/meta-coffee/lib/metacoffee/prettyfier.js:25
            throw "Translation error";
            ^
Translation error

When wrapped with single quotes, I get this special error:

Special error: SyntaxError: unexpected STRING

When wrapped with double quotes, I get this special error:

Special error: SyntaxError: missing ", starting

[duanemaxwell]

I ran into this same problem when build a metacoffee parser for LISP (actually Maru) S-expressions, where backtick is a common syntactic shortcut for creating calls to "quasiquote".

The solution appears to be to add an entry for backtick in the definition of "specials" (used to enumerate characters that require escapes in strings) in ometa-lib, in particular adding the entry

"":"\\"

to escape the character.

[xixixao]

@duanemaxwell PRs are welcome!