Minor complaint by Coverity.

imapsieve plugin: Fixed potential segfault bug caused by shadowing a parameter with a local variable.

Renamed the local variable.
Found by Coverity.

MAIL_FETCH_UIDL_FILE_NAME was removed from core.

imapsieve plugin: Fixed crash occurring when a mailbox is opened for a user before the imap client object is created.

This simplifies the code significantly.
This also removes calls to i_stream_get_data(), which caused problems after its semantics were changed in Dovecot.

lib-sieve: lexer: Adjusted to Dovecot change: i_stream_get_data() no longer returns NULL when returned size = 0.

In effect, this adds PIE and RELRO to binaries.

extprograms plugin: Clarified the language specification regarding handling of filter and execute errors.

extprograms plugin: Execution errors in filter and execute commands did not lead to script termination.

lib-sieve: program client: Fixed bug in handling of result code from remote program (script service).

It was sometimes passed through as data, meaning that the result code was missed.
This transiently resulted in programs seemingly returning invalid result codes, causing an error.

lib-sieve: vacation extension: The sieve_user_email setting is now used in check for implicit delivery.

This means that vacation responses are now also sent for messages that include the sieve_user_email address in one of the relevant headers.

Added assertion to validation function.

Added assertions.

Added assertions.

dovecot-pigeonhole.m4: Make testsuite available when linked against Pigeonhole source tree, even when it is not yet compiled.

imapsieve plugin: During transaction run the synchronized version of the target mailbox was opened too early.

This meant opening a mailbox a second time even if it did not match any mailbox rules.

lib-sieve: edit-mail: Passed FALSE for normalizer argument of message_header_decode_utf8() rather than NULL.

imapsieve plugin: Restructured imap_sieve_run_scripts() function such that the compile error code is never used uninitialized.

lib-sieve: variables extension: Changed declaration of new variables to avoid useless memory allocation.

Also prevents assert failures with new hash_table_insert() assertion against existing entries.
This changes the API for the variables extension.

This prevents trouble with o_stream_nsend_istream() later.

lib-sieve: Changed sieve_extension_override() to use hash_table_update() rather than hash_table_insert().

Due to a Dovecot change this would now cause an assertion failure.