two GCC-3.0 warnings

[Tom Holroyd]

In openssh_cvs/openbsd-compat:

readpassphrase.c: In function `readpassphrase':
readpassphrase.c:116: warning: operation on `ch' may be undefined

The offending line is:
                                ch = ch &= 0x7f;
probably should be:
                                ch &= 0x7f;

In openssh-2.9p2:

readpass.c: In function `read_passphrase':
readpass.c:120: warning: passing arg 2 of `ssh_askpass' discards
qualifiers from pointer target type


It seems to have shut up about the sftp-* printf format warnings.
Seems to work OK...