Add function exports for RPC API to libquilc

[kartik-s]

This PR is a proof-of-concept that demonstrates calling API functions that are currently exposed via the RPC interface through a shared library. An example Python script is included which illustrates usage.

Also see quil-lang/sbcl-librarian#43.

Build instructions on macOS

1. Get a local copy of the SBCL source. This directory will be your SBCL_HOME in later steps.
2. Build SBCL

sh make.sh

If on an Intel Mac, check out the x86-null-tn branch first, then:

sh make.sh --without-compact-instance-header --without-immobile-space --without-immobile-code

3. Build libsbcl.so

sh make-shared-library.sh

4. In quilc/lib/,

SBCL_HOME=<directory from step 1, defaults to ~/sbcl in the Makefile> make

5. Run the example:

SBCL_HOME=<directory from step 1>
PYTHONPATH=. DYLD_LIBRARY_PATH=$SBCL_HOME/src/runtime python3 ./tests/python/rpc_functions.py