Eachleft/eachright + library work.

 1. added vectorizing modifiers for intix ops. These desugar to
builtin combinators eachleft, eachright, which vectorize left
and right arguments, respectively. I.e.
[0, 1, 2] ~+ 10 == 10 +~ [0, 1, 2] == [10, 11, 12]. Only docs
at present are the relevant additions in MeshParser.rats, misc.m
and test_intrinsics.m, unfortunately.

2. Added other library functions: constrain, cutpoints, fruntot,
runtot, starts, trace, tracen. Renamed old trace to tconverge.
Added tests and docs for these.

3. Removed library functions countn, rangen, fromton.

4. Fixed bugs in chunks, pwheren.

5. Stopped inlining sign().