Fix case-sensitivity for device-specific event subscriptions and CCSS

Fix case-sensitivity for device-specific event subscriptions and CCSS

This change fixes case-sensitivity for device-specific subscriptions such that
the technology identifier is case-insensitive while the remainder of the device
string is still case-sensitive.  This should also preserve the original case of
the device string as passed in to the event system.  CCSS is the only feature
affected as it is the only consumer of device-specific event subscriptions.

The second part of this patch addresses similar case-sensitivity issues within
CCSS itself that prevented it from functioning correctly after the fix to the
events system.

This adds a unit test to verify that the event system works as expected.

(closes issue ASTERISK-19422)
Review: https://reviewboard.asterisk.org/r/1780/
........

Merged revisions 357940 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@357941 65c4cc65-6c06-0410-ace0-fbb531ad65f3