This commit contains a new sub-crate called `regex-capi` which provides
a C library called `rure`.
A new `RegexBuilder` type was also added to the Rust API proper, which
permits both users of C and Rust to tweak various knobs on a `Regex`.
This fixes issue #166.
Since it's likely that this API will be used to provide bindings to
other languages, I've created bindings to Go as a proof of concept:
https://github.com/BurntSushi/rure-go --- to my knowledge, the wrapper
has as little overhead as it can. It was in particular important for the
C library to not store any pointers provided by the caller, as this can
be problematic in languages with managed runtimes and a moving GC.
The C API doesn't expose `RegexSet` and a few other convenience functions
such as splitting or replacing. That can be future work.
Note that the regex-capi crate requires Rust 1.9, since it uses
`panic::catch_unwind`.
This also includes tests of basic API functionality and a commented
example. Both should now run as part of CI.
