This commit sets up the infrastructure for supporting various `unicode`
and `perf` features, which permit decreasing binary size, compile times
and the size of the dependency tree.
Most of the work here is in modifying the regex tests to make them
work in concert with the available Unicode features. In cases where
Unicode is irrelevant, we just turn it off. In other cases, we require
the Unicode features to run the tests.
This also introduces a new error in the compiler where by if a Unicode
word boundary is used, but the `unicode-perl` feature is disabled, then
the regex will fail to compile. (Because the necessary data to match
Unicode word boundaries isn't available.)
This commit enables support for compiling regular expressions that can
match on arbitrary byte slices. In particular, we add a new sub-module
called `bytes` that duplicates the API of the top-level module, except
`&str` for subjects is replaced by `&[u8]`. Additionally, Unicode
support in the regular expression is disabled by default but can be
selectively re-enabled with the `u` flag. (Unicode support cannot be
selectively disabled in the standard top-level API.)
Most of the interesting changes occurred in the `regex-syntax` crate,
where the AST now explicitly distinguishes between "ASCII compatible"
expressions and Unicode aware expressions.
This PR makes a few other changes out of convenience:
1. The DFA now knows how to "give up" if it's flushing its cache too
often. When the DFA gives up, either backtracking or the NFA algorithm
take over, which provides better performance.
2. Benchmarks were added for Oniguruma.
3. The benchmarks in general were overhauled to be defined in one place
by using conditional compilation.
4. The tests have been completely reorganized to make it easier to split
up the tests depending on which regex engine we're using. For example,
we occasionally need to be able to write tests specifically for
`regex::Regex` or specifically for `regex::bytes::Regex`.
5. Fixes a bug where NUL bytes weren't represented correctly in the byte
class optimization for the DFA.
Closes#85.
