improved JIT support

added pcre.is_jit_supported() to checking JIT availability

added pcre.get_jit_target() for querying JIT target architecture

added Pattern.set_jit_stack() for adjusting JIT stack size of JIT-optimized patterns
improved unicode handling; v0.4

patterns are now always compiled in UTF-8 mode

previously, compiling a pattern from a str meant that it could not be
used with unicode subjects containing codepoints greater than 255

to minimize encoding overhead, ascii-only strings are detected and
passed diectly to PCRE

strings containing characters 128-255 are encoded using a simple
latin1 -> utf-8 codec (without the intermediate full unicode stage)

objects supporting the buffer interface can now be used as input;
both patterns and subjects support this (unlike re which allows them
for subjects only)

added custom PCRE flags: NOTBOL, NOTEOL, etc.

added testsuite; based on re module tests; included is both mostly
unchanged test_pcre_re_compat.py suite (which fails some re-specifc
tests) as well as test_pcre.py converted to PCRE format