Added support for {SHA} passwords (ticket #50).

Added support for {SHA} passwords (ticket #50).

Note: use of {SHA} passwords is discouraged as {SHA} password scheme is
vulnerable to attacks using rainbow tables.  Use of {SSHA}, $apr1$ or
crypt() algorithms as supported by OS is recommended instead.

The {SHA} password scheme support is added to avoid the need of changing
the scheme recorded in password files from {SHA} to {SSHA} because such
a change hides security problem with {SHA} passwords.

Patch by Louis Opter, with minor changes.