Made utility functions for neatly handing system errors, warnings and notices.

TODO

src/lib-sieve/plugins/include/ext-include-binary.c

src/lib-sieve/sieve-binary.c

src/lib-sieve/sieve-error.c

src/lib-sieve/sieve-error.h

src/lib-sieve/sieve-extensions.c

src/lib-sieve/sieve-script.c

src/plugins/lda-sieve/lda-sieve-plugin.c