Implement the rest of the low-hanging-fruit built-ins

[masak]

This work builds on #117; please rebase on top of master after that one merges. Thanks Rebased.

This PR implements drop, first, whenlet, awhen, each, flip, part, trap, only, >=, <=, floor, ceil, mod, whilet, loop, while, til, for, repeat, poll, accum, nof, drain, ^w, clog2, coin, randlen, rand, wipe, clean, swap, adjoin, pushnew, dedup, insert, sort, best, max, min, even, odd, round, array, vir arr, aref, table, vir tab, tabref, loc isa!tab, tabrem, templates, tem, make, inst. Yep, that's most of the rest.

Notably, a few things were skipped in this PR and will be tackled later:

• chars (Implement the 'chars' builtin #120) — so, waiting with nchar (wait, do we really have to wait? we can mock chars, can't we?)
• err and ccc (Allow dynamic overriding of err #79 and Implement ccc form #80) — so we skip catch for now
• swap (Implement swap #87) because it uses nested bquotes which we don't currently support No, we do support them now (the backquotes were not all that nested), and so swap is here too!
• streams (Implement streams #84) — which is why we skipped withfile, from, to, readall, load and pr

The test suite took its biggest speed hit so far in the project by the work in this PR. The test suite (running under prove with -j4) went from 131 s to 836 s. Similar slowdowns happened with #73 and #96, both of which also added global definitions. Likely, working on speeding up numbers (#91 and #140) would give the biggest payoff after this. (Later edit: Nope, turns out it was #194; faster numbers will probably help too, though.)

Closes #126.
Closes #127.
Closes #129.