Many GDB users always want to display disassembly when they stop by using

something like "display/4i $pc" (or something like this). With LLDB we already
were showing 3 lines of source before and 3 lines of source after the current
source line when showing a stop context. We now improve this by allowing the
user to control the number of lines with the new "stop-line-count-before" and
"stop-line-count-after" settings. Also, there is a new setting for how many
disassembly lines to show: "stop-disassembly-count". This will control how many
source lines are shown when there is no source or when we have no source line
info. 

settings set stop-line-count-before 3
settings set stop-line-count-after 3
settings set stop-disassembly-count 4
settings set stop-disassembly-display no-source

The default values are set as shown above and allow 3 lines of source before 
and after (what we used to do) the current stop location, and will display 4 
lines of disassembly if the source is not available or if we have no debug
info. If both "stop-source-context-before" and "stop-source-context-after" are
set to zero, this will disable showing any source when stopped. The 
"stop-disassembly-display" setting is an enumeration that allows you to control
when to display disassembly. It has 3 possible values:

"never" - never show disassembly no matter what
"no-source" - only show disassembly when there is no source line info or the source files are missing
"always" - always show disassembly.

llvm-svn: 145050