Clean C changes
===============

Removed:
  src/c/jit.c
  src/c/jit.h
  runtime JIT hooks from repl.c and evaluator.c
  runtime compiler/DLL linkage flags
  JIT/code-generation tools
  automatic WinLibs compiler download
  windows-tools.ps1 generation
  SHEN_C_CC and SHEN_C_PYTHON runtime setup
  generated import library requirement

Kept:
  the C evaluator/runtime
  src/c/compiled_kernel.c
  Shen S42 KLambda sources
  ordinary one-time C compilation

Resulting runtime path:

  shen-c.exe -> C evaluator + compiled kernel -> Shen REPL
