This patchs adds and corrects miscellaneous aspects in UDL handling:
* Fix replication of prefix options on creating new language
* Fix cross styling that would take plce when changing an UDL and the active document uses a different UDL
* Now several line/block comment marks can be specified; only the first one was
* Optional parsing of nested comment blocks
* Keywords may now start or contain any character, even though they might look like operators or numbers
* If the minus sign is an operator, it is coloured as a number if detected as part of a number
* Surrounding a keywords with double quotes will allow it to have multiple parts. One space is equivalent to any number of spaces and tabs.
* In prefix mode, if a multiple part keyword ends with a trailing space, the next word will be part of highlighted text. Such a trailing space is ignored if prefix mode is off.
This patch merges and supersedes patches #2960313, 2960358, 2960415, 2960872, 2962293, 3047328