test coverage for std.regexp

[Don Clugston]

std.regexp currently has very poor test coverage (about 50%). The code 
below greatly increases the coverage (to over 80%), but they are not 
actual tests, other than exercising the parsing code. Perhaps someone 
with some spare time might add some asserts and more sensible test 
strings to turn them into actual tests so that they can be added to Phobos?

-------
unittest {
// TODO: Actually check the return values of these searches!
     auto m = regexp.search("aBC r s", `bc\x20r[\40]s`, "i");
     assert(m.pre=="a");
     assert(m.match(0)=="BC r s");
     auto m2 = regexp.search("7xxyxxx", `^\d([a-z]{2})\D\1`);
     assert(m2.match(0)=="7xxyxx");
     // Just check the parsing.
     auto m3 = regexp.search("dcbxx", `ca|b[\d\]\D\s\S\w-\W]`);
     auto m4 = regexp.search("xy", `[^\ca-\xFa\r\n\b\f\t\v\0123]{2,485}$`);
     auto m5 = regexp.search("xxx", `^^\r\n\b{13,}\f{4}\t\v\u02aF3a\w\W`);
     auto m6 = regexp.search("xxy", `.*y`);
     assert(m6.match(0)=="xxy");
     auto m7 = regexp.search("QWDEfGH", "(ca|b|defg)+", "i");
     assert(m7.match(0)=="DEfG");
     auto m8 = regexp.search("dcbxx", `a?\B\s\S`);
     auto m9 = regexp.search("dcbxx", `[-w]`);
     auto m10 = regexp.search("dcbsfd", 
`aB[c-fW]dB|\d|\D|\u012356|\w|\W|\s|\S`, "i");
     auto m11 = regexp.search("dcbsfd", `[]a-]`);
     m.replaceOld(`a&b\1c`);
     m.replace(`a$&b$'$1c`);
}