Extended sievec command to allow compiling an entire directory.

doc/man/sievec.1

src/lib-sieve-tool/sieve-tool.c

src/lib-sieve-tool/sieve-tool.h

src/lib-sieve/sieve-script-private.h

src/lib-sieve/sieve-script.c

src/lib-sieve/sieve-script.h

src/lib-sieve/sieve.c

src/lib-sieve/sieve.h

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

src/sieve-tools/sieve-test.c

src/sieve-tools/sievec.c

src/testsuite/testsuite-script.c

src/testsuite/testsuite.c