Enotify: shielded most of the method API from compiler internals.

src/lib-sieve/plugins/enotify/cmd-notify.c

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

src/lib-sieve/plugins/enotify/ext-enotify-common.h

src/lib-sieve/plugins/enotify/ntfy-mailto.c

src/lib-sieve/plugins/enotify/sieve-ext-enotify.h

src/lib-sieve/sieve-actions.c

src/lib-sieve/sieve-actions.h

src/lib-sieve/sieve-error.c

src/lib-sieve/sieve-error.h

src/lib-sieve/sieve-result.c

src/lib-sieve/sieve-result.h

src/lib-sieve/sieve-script.c

src/lib-sieve/sieve-script.h