Improved runtime trace debugging output for core Sieve language.

TODO

src/lib-sieve/cmd-discard.c

src/lib-sieve/cmd-keep.c

src/lib-sieve/cmd-redirect.c

src/lib-sieve/cmd-stop.c

src/lib-sieve/ext-envelope.c

src/lib-sieve/ext-fileinto.c

src/lib-sieve/ext-reject.c

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

src/lib-sieve/sieve-code.c

src/lib-sieve/sieve-interpreter.c

src/lib-sieve/sieve-match.c

src/lib-sieve/sieve-match.h

src/lib-sieve/sieve-runtime-trace.c

src/lib-sieve/tst-address.c

src/lib-sieve/tst-exists.c

src/lib-sieve/tst-header.c

src/sieve-tools/sieve-test.c