Remove emscripten support

[kulp]

Support for running the tenyr tools under emscripten has been a useful experiment in portability, and a similar capability (or compiling to Wasm) should be resurrected in time. When the online demo was removed in 5231a1c, I said

On the other hand, building for node.js (via asm.js or wasm) is a valuable capability that will be maintained for 1.0.

and if possible this intention should be maintained.

However, emscripten support has been broken for a while (insofar as I did not keep up with breakages introduced by newer emscripten versions), and the natural use of NODERAWFS is not compatible with the current Make-based test harness (which tries to use absolute paths).

Making emscripten work again with the current build system is feasible, but would work against #50 and #53, which are more important for v1.0.0 support than emscripten support is. After those two issues are resolved, we can try to reinstate node.js support (or some other emscripten-like target) for v1.0.0 if time permits.

[codecov]

Codecov Report

Merging #92 (ea37de4) into develop (5e3c059) will decrease coverage by 0.0%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           develop     #92     +/-   ##
=========================================
- Coverage     96.6%   96.6%   -0.1%     
=========================================
  Files           35      34      -1     
  Lines         2652    2650      -2     
  Branches       468     468             
=========================================
- Hits          2563    2561      -2     
  Misses          70      70             
  Partials        19      19             

Impacted Files	Coverage Δ
src/tsim.c	94.9% <ø> (ø)

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