Progress OpenEdge 11.6 added a new C-like single-line comment syntax; such
comments begin with `//` and proceed to the end of the line.
Add a new syntax group `ProgressLineComment` to implement highlighting for this
syntax. Rename the existing group from `ProgressComment` to
`ProgressBlockComment`, and introduce a cluster named `ProgressComment` to
encapsulate both.
closes: #15339
Signed-off-by: Daniel Smith <daniel@rdnlsmith.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
