Fixed a few bugs in the "step in" thread plan logic.

Added a "step-in-target" flag to "thread step-in" so if you have something like:

Process 28464 stopped
* thread #1: tid = 0x1c03, function: main , stop reason = breakpoint 1.1
    frame #0: 0x0000000100000e08 a.out`main at main.c:62
   61         
-> 62         int A6 = complex (a(4), b(5), c(6)); // Stop here to step targetting b and hitting breakpoint.
   63             

and you want to get into "complex" skipping a, b and c, you can do:

(lldb) step -t complex
Process 28464 stopped
* thread #1: tid = 0x1c03, function: complex , stop reason = step in
    frame #0: 0x0000000100000d0d a.out`complex at main.c:44
   41     
   42     int complex (int first, int second, int third)
   43     {
-> 44         return first + second + third;  // Step in targetting complex should stop here
   45     }
   46         
   47     int main (int argc, char const *argv[])

llvm-svn: 170008