notmuch: use the Maildir if NotmuchDefaultUri is unset

[kzak@redhat.com: - cleanup code, add note to README.notmuch]

Signed-off-by: Karel Zak <kzak@redhat.com>
notmuch: sync flags for all duplicate messages

Signed-off-by: Karel Zak <kzak@redhat.com>
format: support optional modifier for g (notmuch labels)

Used in index_format like this %?g?(%g)? will show nothing if there are
no notmuch labels, eg. in mixed mail setups.

Signed-off-by: David Sterba <dsterba@suse.cz>
notmuch: print read progress of a query

Signed-off-by: David Sterba <dsterba@suse.cz>
mutt_notmuch: nm_db_limit option defines a default limit
notmuch: add note about nm_db_limit to README

Signed-off-by: Karel Zak <kzak@redhat.com>
notmuch: fix typo

Reported-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Karel Zak <kzak@redhat.com>
notmuch: add nm_query_type config file option

Signed-off-by: Karel Zak <kzak@redhat.com>
notmuch: add notmuch_{query,message}_destroy to DB checker

Reported-by: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Karel Zak <kzak@redhat.com>
Update Italian translation
Do not use SASL for login unless AUTH=LOGIN is advertised (closes #3556)
check_charset: check for NULL before calling strtok_r (closes #3326)

Otherwise, if strtok_r cannot handle NULL an empty *charset setting will segfault
gnutls:tls_compare_certificates: check strstr for failure (closes #3547)

A malformed certificate file could cause strstr to return an unhandled NULL.
Thanks to hhorak for the proposed patch. This one is similar but avoids using
memmem for the first time (I am not sure about its portability).
Fix some spelling errors (closes #3493)
silence some style warnings
Set text_flowed after send-hook has been applied (closes #3550)
Do not use stack-allocated space for BUFFERs

It will cause mutt_buffer_* to segfault if it needs to grow the space.
Thanks to Steve Losh for discovering the issue. I have done some simple
grepping to find other cases, but some may remain.
Split mutt_buffer_new out of mutt_buffer_init.

Currently, no callers were providing a non-NULL buffer to
mutt_buffer_init, and splitting it will allow more sane semantics for
buffer allocation, initialization, and destruction in a later patch.
mutt_buffer_init: just memset the buffer (closes #3588)

This was meant to be part of the previous commit.
Add compiler and configure info to mutt -v output (closes #3537)

Makefile(.am) updated to produce conststrings.c, which contains
C strings representing:

* the compiler's own version information;
* the CFLAGS value from the Make environment
* the ./configure options

main.c is updated to print them when running 'mutt -v'.

txt2c.sh is added to produce conststrings.c. txt2c.sh uses a compiled
txt2c binary if possible, for complete fidelity to the source strings
in whatever encoding they may use.  If txt2c is not available (could
not be compiled, or was not compiled natively) it falls back on a shell
function to approximate the output using sed and tr.