Fix non ES5 compliant regexp

[zetaben]

ES5 appears to require that { be escaped when not used as part of a quantifier. While this works fine in browsers it appears to choke less lenient runtimes (e.g. Duktape).

A similar case is discussed in Duktape (svaarala/duktape#69 and svaarala/duktape#74).

Please find attached a simple Duktape-powered C file that tries to parse the given argument file. test.c.zip

Compile and run using:

$ gcc -std=c99 -o test test.c duktape-1.3.1/src/duktape.c -I duktape-1.3.1/src/  -lm && ./test mocha/mocha.js

When choking it produces a:
eval failed: SyntaxError: invalid regexp quantifier (unknown char) (line 5755)
when the parsing is fine it will produce (because I did not setup a complete environment):
eval failed: ReferenceError: identifier 'window' undefined

[jbnicolai]

Looks good to me, thanks for the effort!

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