Cleaned up test and core extension implementations.

sieve/tests/encoded-character.sieve

src/lib-sieve/cmd-if.c

src/lib-sieve/cmd-redirect.c

src/lib-sieve/ext-encoded-character.c

src/lib-sieve/ext-envelope.c

src/lib-sieve/ext-fileinto.c

src/lib-sieve/ext-reject.c

src/lib-sieve/sieve-interpreter.c

src/lib-sieve/tst-address.c

src/lib-sieve/tst-allof.c

src/lib-sieve/tst-anyof.c

src/lib-sieve/tst-exists.c

src/lib-sieve/tst-header.c

src/lib-sieve/tst-not.c

src/lib-sieve/tst-size.c