JavaScript: Improve support for contextual keywords as identifiers

[b4n]

As the title says, better handle contextual keywords as function, property and method identifiers.

All these are probably fairly rare, but some did appear in e.g. a minified jQuery, leading to emitting null tags. Now, only the actually empty-named property it contains (""://…) leads to emitting a null tag.

This mostly builds up the get and set handling for all contextual keywords valid in these situations.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.41%. Comparing base (07cbb8c) to head (eb830ef).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3993   +/-   ##
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  Coverage   85.40%   85.41%           
=======================================
  Files         235      235           
  Lines       56636    56639    +3     
=======================================
+ Hits        48371    48376    +5     
+ Misses       8265     8263    -2     

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[masatake]

About the new test case, adding args.ctags file with contents --sort=no makes expected.tags easier to read.

[b4n]

About the new test case, adding args.ctags file with contents --sort=no makes expected.tags easier to read.

I would agree in general, but I think that in the case of contextual.d it's pretty handy that it's sorted so you can easily see that there is basically 4 identical symbols of each name (but for the instances and class names, and the length property I could just get rid of as well).
If you prefer sorted though I'll add it not problem.

For the other test case sure, yet it's already sorted in the source so won't change a thing for now :)

[masatake]

@jafl I'm going to merge this as you approved. So we can work on the topic discussed at #3363.