Experiment to evaluate concrete terms in booster instead of llvm library

Fully concrete terms are currently sent to the LLVM backend library, which may (or may not) represent a considerable fraction of execution time.
Several ideas combined may get us some performance improvements:

1. Implement a broad selection of hooked functions for frequently-used data types
2. Decide in some way dynamically how and whether to call the LLVM library:

• Export hooks instead of term API (plus hooked-type API) from LLVM library.
  • Hopefully thread-safe by construction
  • will keep calling marshalling more often, but hopefully very efficient small functions
• be more semantics-independent: not recompiling a specific definition but rather have a generic llvm library
  • amounts to exporting the hooks when taken to the extreme
  • however, there may be cases of generic functions doing useful work on symbolic input
• hook analysis
  a) analyse function equations for which hooks they use (transitively, bottom-up)
  b) synthesize term attribute to get a list of hooks
  c) only call llvm if there are hooks not implemented in booster