Revamp man pages for recent changes

Revamp man pages for recent changes

New functions documented:
* crypto_sign (incremental interface)
* crypto_verify16/32/64

Deprecated functions:
* crypto_memcmp
* crypto_zerocmp

Other changes:
* crypto_lock and crypto_aead_lock pages have been merged as they are
  closer to each other in complexity than the incremental and low-level
  crypto_lock interface.

The crypto_memcmp and crypto_zerocmp pages have not been removed in case
people still have references to those functions in their code and are
wondering what the canonical replacement is.