CommandObjectProcess was recently changed to automatically use the platform

to launch a process for debugging. Since this isn't supported on all platforms,
we need to do what we used to do if this isn't supported. I added:

    bool
    Platform::CanDebugProcess ();
    
This will get checked before trying to launch a process for debugging and then
fall back to launching the process through the current host debugger. This
should solve the issue for linux and keep the platform code clean.

Centralized logging code for logging errors, warnings and logs when reporting
things for modules or symbol files. Both lldb_private::Module and 
lldb_private::SymbolFile now have the following member functions:

    void                    
    LogMessage (Log *log, const char *format, ...);

    void
    ReportWarning (const char *format, ...);

    void
    ReportError (const char *format, ...);

These will all output the module name and object (if any) such as:

    "error: lldb.so ...."
    "warning: my_archive.a(foo.o) ...."
    
This will keep the output consistent and stop a lot of logging calls from 
having to try and output all of the information that uniquely identifies
a module or symbol file. Many places in the code were grabbing the path to the
object file manually and if the module represented a .o file in an archive, we
would see log messages like:

    error: foo.a - some error happened

llvm-svn: 145219