Improved address validation significantly.

sieve/errors/out-address-errors.sieve

src/lib-sieve/Makefile.am

src/lib-sieve/cmd-redirect.c

src/lib-sieve/plugins/vacation/cmd-vacation.c

src/lib-sieve/sieve-address.c

src/lib-sieve/sieve-address.h

src/lib-sieve/sieve-validator.h