Adds explicit Rational{BigInt} convert method. Indirectly addresses #6712.
ignore ARCH varianle in env. fix #7433
Merge pull request #7505 from simonbyrne/big-rational

Adds explicit Rational{BigInt} convert method
better help for rationalize()
Fixed a typo of function name, besselkx(nu, x).
make next(::UTF8String, i) a bit more robust. fixes #7525

skip 1 byte when returning an invalid character, because the data might be
Latin-1, and the result is not well-defined anyway.

the previous performance hack in next() is no longer necessary, since
returning tuples is now fast.
Merge pull request #7526 from yomichi/patch-1

Fixed a typo of function name, besselkx(nu, x).