despite the large changes, this commit only moves functions

despite the large changes, this commit only moves functions
around so that functions belonging to the same group are
close to each other.

At the beginning of each group i have added a bit of documentation
to explain what the group does and what is the typical flow - basically,
all i have learned by code inspection over the past few days should
be documented for you to read.

I have not put many doxygen annotations just because i am not
sure what are the proper ones. Hopefully some doxygen experts will jump in.

Next on the plate: try to figure out how "struct eventqent"
are supposed to work.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@45582 65c4cc65-6c06-0410-ace0-fbb531ad65f3