lib-sieve: Fixed various bool vs. int/pointer mixups.

src/lib-sieve/mcht-is.c

src/lib-sieve/sieve-address-parts.c

src/lib-sieve/sieve-address.c

src/lib-sieve/sieve-binary-file.c

src/lib-sieve/sieve-binary.c

src/lib-sieve/sieve-code.c

src/lib-sieve/sieve-commands.c

src/lib-sieve/sieve-parser.c

src/lib-sieve/sieve-result.c

src/lib-sieve/sieve-storage.c

src/lib-sieve/sieve-stringlist.c

src/lib-sieve/sieve.c

src/lib-sieve/tst-exists.c