Fixed bugs in validation error handling and fixed bugs in dynamic argument support.

src/lib-sieve/cmd-redirect.c

src/lib-sieve/ext-envelope.c

src/lib-sieve/ext-fileinto.c

src/lib-sieve/ext-reject.c

src/lib-sieve/plugins/body/tst-body.c

src/lib-sieve/plugins/imapflags/ext-imapflags-common.c

src/lib-sieve/plugins/imapflags/tst-hasflag.c

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

src/lib-sieve/plugins/variables/cmd-set.c

src/lib-sieve/plugins/variables/ext-variables-common.c

src/lib-sieve/plugins/variables/tst-string.c

src/lib-sieve/plugins/variables/variables.sieve

src/lib-sieve/sieve-validator.c

src/lib-sieve/tst-address.c

src/lib-sieve/tst-exists.c

src/lib-sieve/tst-header.c

src/lib-sieve/tst-size.c