Fix crash when parsing some heavily nested statements in AEL on reload.

Fix crash when parsing some heavily nested statements in AEL on reload.

Due to the recursion used when compiling AEL in gen_prios, all the stack space
was being consumed when parsing some AEL that contained nesting 13 levels deep.
Changing a few large buffers to be heap allocated fixed the crash, although I
did not test how many more levels can now be safely used.

(closes issue #16053)
Reported by: diLLec
Tested by: jpeeler

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@271399 65c4cc65-6c06-0410-ace0-fbb531ad65f3