lib-sieve: sieve-extensions - Use int for load() func status result

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

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

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

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

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

src/lib-sieve/plugins/imap4flags/ext-imap4flags.c

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

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

src/lib-sieve/plugins/mime/ext-extracttext.c

...ib-sieve/plugins/spamvirustest/ext-spamvirustest-common.c

...ib-sieve/plugins/spamvirustest/ext-spamvirustest-common.h

src/lib-sieve/plugins/subaddress/ext-subaddress.c

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

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

src/lib-sieve/plugins/vacation/ext-vacation-seconds.c

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

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

...eve/plugins/vnd.dovecot/environment/ext-vnd-environment.c

...-sieve/plugins/vnd.dovecot/report/ext-vnd-report-common.c

...-sieve/plugins/vnd.dovecot/report/ext-vnd-report-common.h