astdb: crash in sqlite3 during shutdown

When Asterisk is shut down, the astdb_atexit() function releases
(finalize) the previously initiated (prepared) SQL statements in
sqlite3.  Another thread making a subsequent request can cause a
crash in sqlite3.  This patch eliminates that issue by resetting
the statement pointer after it is released/cleared.  The sqlite3
code detects the null pointer, and aborts the operation cleanly.

(closes issue AST-1265)
Reported by: Alexander Hömig
(closes issue ASTERISK-22350)
Reported by: Birger "WIMPy" Harzenetter
Review: https://reviewboard.asterisk.org/r/3078/
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Merged revisions 404344 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@404345 f38db490-d61c-443f-a65b-d21fe96a405b
Voicemail: Remove mailbox identifier format (box@context) assumptions in the system.

This change is in preparation for external MWI support.

Removed code from the system for normal mailbox handling that appends
@default to the mailbox identifier if it does not have a context.  The
only exception is the legacy hasvoicemail users.conf option.  The legacy
option will only work for app_voicemail mailboxes.  The system cannot make
any assumptions about the format of the mailbox identifer used by
app_voicemail.

chan_sip and chan_dahdi/sig_pri had the most changes because they both
tried to interpret the mailbox identifier.  chan_sip just stored and
compared the two components.  chan_dahdi actually used the box
information.

The ISDN MWI support configuration options had to be reworked because
chan_dahdi was parsing the box@context format to get the box number.  As a
result the mwi_vm_boxes chan_dahdi.conf option was added and is documented
in the chan_dahdi.conf.sample file.

Review: https://reviewboard.asterisk.org/r/3072/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@404348 f38db490-d61c-443f-a65b-d21fe96a405b
res_fax.c: crash on framehook with no dsp in fax detect

In fax_detect_framehook() a null pointer reference can occur where a
voice frame is processed but no dsp is attached to the fax detection
structure.  The code block that rejects frames that detection cannot
be processed on is checking for dsp but falls through when it should
instead return, as this change implements.

(closes issue ASTERISK-22942)
Reported by: adomjan
Review: https://reviewboard.asterisk.org/r/3076/
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Merged revisions 404351 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@404352 f38db490-d61c-443f-a65b-d21fe96a405b
udptl: Dead code elimination. ast_udptl_bridge was not used.

Removing dead code starting with ast_udptl_bridge() eliminated the code in
this change.

Note: This code has actually been dead since Asterisk v1.4 when it was
first put in.

Review: https://reviewboard.asterisk.org/r/3079/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@404354 f38db490-d61c-443f-a65b-d21fe96a405b