Fix #4283: error message for implicit call

[helixbass]

Fixes #4283

@lydell is this what you had in mind? I made the error message unexpected implicit function call, and it points to the identifier that was being implicitly called (almost seems like it should point to the space between the implicit function and its first arg, but this probably clarifies the error sufficiently?)

[lydell]

I don't remember exactly what I had in mind about a year ago, but this seems great!

[GeoffreyBooth]

Should this have been merged into master?

[lydell]

Yes, it's harmless.

[GeoffreyBooth]

@lydell @helixbass when I merge this into 2 and resolve conflicts, then run cake build:except-parser && cake test, I get:

/Users/Geoffrey/Sites/coffeescript/lib/coffeescript/coffeescript.js:44
        throw helpers.updateSyntaxError(err, code, options.filename);
        ^

Cakefile:46:33: error: unexpected end of input
  spawnNodeProcess ['bin/coffee'].concat(args), 'stderr', (status) ->
                                ^

See https://github.com/GeoffreyBooth/coffeescript/tree/merge-error-message-implicit-call (I didn’t check in lib, so that you could build the compiler).

[helixbass]

@GeoffreyBooth I merged master into 2 on my 2_merge_master branch and opened #4597. I think it was a question of how rewriter.coffee was merged. But also found that the test case from #4585 needed to be updated b/c of #4493 grammar changes. As I commented in #4597, my only question regarding the merge conflicts was whether the "CoffeeScript 2 is coming..." line in documentation/sections/introduction.md should be preserved or not, as of now I've deleted it