Fix trailingFunctionCommas bugs

[mourner]

• Fixes #192 (infinite loop on commented multiline calls without trailing comma).
• Fixes #175 (revoming a comma outside the scope of a function call).

cc @adrianheine

[mourner]

Both bugs happened because */ is two characters while \n is one character, so getting it's index + 1 and then incrementing the index again made us skip the closing parens of a call if there was no white space before it in the \n case, essentially making the code look for "trailing commas" way past the actual call, either freezing or finding a comma from a different context.

[adrianheine]

Thanks!