Review #242091: Usability: Stepping through JDK sources does not display local variables

Please review the fix of bug
https://netbeans.org/bugzilla/show_bug.cgi?id=242091

Description:
When the source code (e.g. JDK sources) is compiled without -g option, 
variable information is not available in class files. The bug suggest, 
that this fact should be reported more expressively. The message 
"Variable information not available, source compiled without -g option" 
should be more visible in Variables window and tooltip and variable 
value that says "<variable> is not a known variable in the current 
context." is not much helpful to realize why debugger does not find it.

Solution:
We display the warning message "Variable information not available, 
source compiled without -g option" in red bold so that it can not be missed.
The tooltip and value message is changed to better describe what's going on.

Impact assesment:
Usability

Risk:
Very low

The bugfix was reviewed and verified.

http://hg.netbeans.org/main-silver/rev/cd497a606726

Thanks,
Martin