- Added .gitignore.
- Adapted release.sh script to git.
- Removed :version from cffi.asd. Release tarballs now get the release
  version inserted into the tarball's cffi.asd.
- Update manual with git info.

Define the :fsbv package.  Define types that are defined in the
library.  Define structs: ffi-type (ffi_type) is defined using the
groveller because it has a name after the "typedef struct" in ffi.h;
ffi-cif (ffi_cif) is defined by hand in structs.lisp because it
doesn't, so gcc can't handle it.  Everything compiles and load in
linux/amd64.