Remove ErmBuffer::Parser.make_hash

[vzvu3k6k]

There is no need to make hashes of INDENT_KW, BACKDENT_KW,
BEGINDENT_KW, POSTCOND_KW and PRE_OPTIONAL_DO_KW.
Only include? is called for them.

[zenspider]

Make_hash is there to make the include? call O(1) instead of O(n). Dunno if it matters for hashes this size tho. Benchmark it?

[vzvu3k6k]

make the include? call O(1) instead of O(n)

Ah, I overlooked it...

I've benchmarked it and found it matters even for the smallest array. The difference is not so big (make_hash version of INDENT_KW is 1.77e-6 sec faster in each time on average in my env), but it may actually matters when processing a very big file. And as the cost of make_hash is vanishingly low (benchmark), I think it is better to leave it as it is.

Thank you for your trouble.