Fix SNMP gitignore files
Use erlang:demonitor(Ref, [flush]) where applicable
Remove unused Postscript files
Merge branch 'lh/demonitor-flush/OTP-11039' into maint

* lh/demonitor-flush/OTP-11039:
  Use erlang:demonitor(Ref, [flush]) where applicable
Remove the "coding: utf-8" comment from all Erlang source files
Convert XML files to UTF-8
[snmp/agent] Preliminary change to the mib-server tree-type
[snmp/agent] New behaviour module (snmpa_mib_data) and two impl mods

The old mib-server data module (snmpa_mib_data) has been changed into
a behaviour module. The old implementation is now instead in a new
module snmpa_mib_data_tree1. A new backend module has been added,
still only very preliminary, snmpa_mib_data_tree2.
[snmp/agent] Renamed the mib_data (backend) modules

Renmed the two backend modules:

       snmpa_mib_data_tree1.erl -> snmpa_mib_data_tttn.erl
       snmpa_mib_data_tree2.erl -> snmpa_mib_data_ttln.erl

TTTN - TupleTreeTupleNodes
TTLN - TupleTreeListNodes
[snmp/agent] Preliminary doc update regarding mib_data behaviour
[snmp/agent] Some minor mib_data behaviour changes
[snmp/agent] Some minor documentation additions
[snmp/agent] Added some description and the behaviour attribute
[snmp/agent] Fixed snmpa_mib_data behaviour and related

Finalized snmpa_mib_data behaviour. Updated mib-server and
tttn module accordingly. Also assigned proper version, updated
app and appup files.
[snmp] Added doc/index.html file to git ignore
[snmp/agent] Updated documentation and release notes
[snmp/agent] Fixed some test cases
[snmp] Added rules to git-ignore to not see patch apply result files
[snmp/agent] Add comment to TTLN file instead of deleting it
[snmp/agent] Improved mib-server data module overview text