Enable macros in 1.8 to find the next highest "h" extension in a context, like in 1.4.

This change restores functionality that was present in 1.4, when AEL macros
were implemented with the Macro dialplan application.  Macros are fraught with
functionality issues, because they consume a large portion of the underlying
application stack.  This limits the ability of AEL users to call many layers
of subroutines, an issue which Gosub does not have (originally tested to
100,000 levels deep).  Therefore, starting in 1.6.0, AEL macros were
implemented with Gosub.

However, there were some implicit behaviors of Macro, which were not replicated
at the same time as with the transition to Gosub, one of which is documented in
the related issue.  In particular, the "h" extension is designed to execute not
in the Macro context, but in the topmost calling context.  Due to legacy issues
with a misapplied bugfix many years ago, when a macro exited in 1.4, it looks
in all calling contexts, bubbling up from the deepest level until it finds an
"h" extension.

Since AEL hides the complexity of the underlying dialplan logic from the AEL
programmer, it's reasonable to assume that this behavior should not change in
the transition from Asterisk 1.4 LTS to Asterisk 1.8 LTS, lest we break
working AEL configurations in the transition to Asterisk 1.8 LTS.  This fix
is the result, which implements a search for the "h" extension in all calling
Gosub contexts.

Fixes ASTERISK-19336

Patch: 20120308__ael_bugfix_for_trunk__2.diff (License #5003) by Tilghman Lesher
	(with slight modifications for 1.8)

Tested by: Johan Wilfer

Review: https://reviewboard.asterisk.org/r/1776/
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Merged revisions 358810 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 358811 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@358812 65c4cc65-6c06-0410-ace0-fbb531ad65f3