medix_index: Display errors when library calls fail

Based on feedback from ipengineer in #asterisk, when the media indexer
cannot access a sound file on the system (or otherwise fails) Asterisk
displays a "Cannot frob file" error but fails to tell you why. This is
especially problematic as the media_indexer failing will rpevent Asterisk
from starting, as it is in the core.

We now display the errno error messages so folks can figure out what they've
done wrong.
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Merged revisions 402285 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@402286 f38db490-d61c-443f-a65b-d21fe96a405b
core/loader: Don't call dlclose in a while loop

For awhile now, we've noticed continuous integration builds hanging on CentOS 6
64-bit build agents. After resolving a number of problems with symbols, strange
locks, and other shenanigans, the problem has persisted. In all cases, gdb
shows the Asterisk process stuck in loader.c on one of the infinite while loops
that calls dlclose repeatedly until success.

The documentation of dlclose states that it returns 0 on success; any other
value on error. It does not state that repeatedly calling it will eventually
clear those errors. Most likely, the repeated calls to dlclose was to force a
close by exhausting the references on the library; however, that will never
succeed if:
(a) There is some fundamental error at work in the loaded library that
    precludes unloading it
(b) Some other loaded module is referencing a symbol in the currently loaded
    module

This results in Asterisk sitting forever.

Since we have matching pairs of dlopen/dlclose, this patch opts to only call
dlclose once, and log out as an ERROR if dlclose fails to return success. If
nothing else, this might help to determine why on the CentOS 6 64-bit build agent
things are not closing successfully.

Review: https://reviewboard.asterisk.org/r/2970
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Merged revisions 402287 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 402288 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 402289 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@402290 f38db490-d61c-443f-a65b-d21fe96a405b