Dovecot core doesn't have copyright notices in header files.

Clang -Wvargargs complained about passing a bool argument to va_start().

perl -i -pe 's/unsigned int ([^,:;]+):1;/bool $1:1;/' **/*.[ch]

This change matches a similar change in Dovecot for IMAP/POP3.
Also includes other small changes that make ManageSieve match IMAP implementation a little more closely.

Enforced ManageSieve protocol syntax better with some of the commands; some commands still allowed spurious extra arguments.