Move the SourceManager from the Debugger to the Target. That way it can store the per-Target default Source File & Line.

Set the default Source File & line to main (if it can be found.) at startup.  Selecting the current thread & or frame resets 
the current source file & line, and "source list" as well as the breakpoint command "break set -l <NUM>" will use the 
current source file.

llvm-svn: 139323

lldb/source/API/SBSourceManager.cpp

@@ -61,8 +61,7 @@ SBSourceManager::DisplaySourceLinesWithLineNumbers
 
     if (file.IsValid())
     {
-        return m_opaque_ptr->DisplaySourceLinesWithLineNumbers (NULL,
-                                                                *file,
+        return m_opaque_ptr->DisplaySourceLinesWithLineNumbers (*file,
                                                                 line,
                                                                 context_before,
                                                                 context_after,