return true for exactly the characters treated as whitespace by their flex
scanners. Per report from Victor Snezhko and subsequent investigation.
Also fix a passel of unsafe usages of <ctype.h> functions, that is, ye olde
char-vs-unsigned-char issue. I won't miss <ctype.h> when we are finally
able to stop using it.
Few cleanups and couple of new things:
- add SHA2 algorithm to older OpenSSL
- add BIGNUM math to have public-key cryptography work on non-OpenSSL
build.
- gen_random_bytes() function
The status of SHA2 algoritms and public-key encryption can now be
changed to 'always available.'
That makes pgcrypto functionally complete and unless there will be new
editions of AES, SHA2 or OpenPGP standards, there is no major changes
planned.
