Make deferred init works for rollup

[megabuz]

I've tried to use ohm-js with rollup and I've faced the issue of circular dependency in pexprs.js.

Based on specification all imports should be evaluated prior to the body of module doing the importing, so in case when pexprs requires bunch of extensions, e.g. pexprs-allowsSkippingPrecedingSpace, rollup includes these extensions in the final bundle before pexprs. However they depend on pexprs and I'm receiving error similar to #185 (comment)

In this PR I moved body of pexprs to separate file. It should make rollup module ordering work correctly.

[megabuz]

I found several similar problems, I'm trying to fix them

[megabuz]

So upon further testing I found that any require should be able to execute correctly before module that calls it.
I moved some deferred inits from main.js and Semantics.js to separate files to break this ordering dependency

[pdubroy]

@megabuz Thanks for taking this on! Is this PR ready for review? It seems to contain some unrelated changes. Can you trying rebasing your branch onto master?

[megabuz]

@pdubroy it is ready to review.
Could you point out unrelated changes? All changes should be related to breaking circular dependencies

[pdubroy]

@megabuz Great! And sorry — my mistake, at a quick glance I thought some of these changes were related to something else.

Thanks again, and I'll try to review this in the next day or two.

[pdubroy]

Awesome, thanks for doing this! It looked good to me so I've gone ahead and merged it.

[pdubroy]

Just published v16.1.1 which contains these changes.