about clasp (a new common lisp) support

[Qian Yun]

With the recent release of clasp-2.0.0, I tried to use it to build
FriCAS again, and I almost succeed.

You can see the full patch here:

https://github.com/oldk1331/fricas/commit/425663cfa9d777f73ef9a63a3c5325bcd0cbd91c.patch

The small remaining problem is: FFI calls with string as argument.
Currently only one such function is used during building:
remove_directory. But luckily there's shell version fallback.

The details are:

Current CLASP-FFI is very minimal, it is built to interface CFFI.
It doesn't support interoperability between Lisp string and C string
like SBCL, it doesn't support WITH-CSTRING like ECL.

So we have to either implement many code to support it, or to use
CFFI directly, which can be complicated because of ASDF/quicklisp.
But it can be an opportunity to support other Lisp libraries, e.g.
jupyter kernels.


Some more notes regarding current CLASP-FriCAS: the build requires
a long time -- it takes a long time in the final step to build
databases. The build takes lots of disk space. The speed is not
great so far -- it takes 22 minutes to do "make check" while the
SBCL version takes 1 minute.

- Qian