Fix issue #1 - define PERL_STATIC_INLINE if not already defined
fix macro redefinition issue in perl5.18 and later

Perl 5.18 already provides these defines (no wonder, they come from hv_func.h), so
avoid defining them twice. We probably actually would also get other collisions if
Perl 5.18 or later were built with SIPHASH_2_4. We leave that issue for later.
update .gitignore
Bump version to 0.05