Allow (CV=) after a literal string

Natural allows the use of dynamic control variables during INPUT and WRITE.

BUT: the use of those (CV=<control_variable>) is restricted to a variable, not to a literal text.

If you want to have a different visual behavior for a string, you must move/copy this string into a variable, and use that variable followed by (CV=<control_variable>)

whereas something like

INPUT #answer
'PF1: option_1'
'PF10: Only for administrator' (CV=#CV_ADMIN)

must be coded now as:

#PF10_TXT := 'PF10: Only for administrator'
INPUT #answer
'PF1: option_1'
#PF10_TXT (CV=#CV_ADMIN)