Added the capability to specify a one-liner Python script as the callback

command for a breakpoint, for example:

(lldb) breakpoint command add -p 1 "conditional_break.stop_if_called_from_a()"

The ScriptInterpreter interface has an extra method:

    /// Set a one-liner as the callback for the breakpoint command.
    virtual void 
    SetBreakpointCommandCallback (CommandInterpreter &interpreter,
                                  BreakpointOptions *bp_options,
                                  const char *oneliner);

to accomplish the above.

Also added a test case to demonstrate lldb's use of breakpoint callback command
to stop at function c() only when its immediate caller is function a().  The
following session shows the user entering the following commands:

1) command source .lldb (set up executable, breakpoint, and breakpoint command)
2) run (the callback mechanism will skip two breakpoints where c()'s immeidate caller is not a())
3) bt (to see that indeed c()'s immediate caller is a())
4) c (to continue and finish the program)

test/conditional_break $ ../../build/Debug/lldb
(lldb) command source .lldb
Executing commands in '.lldb'.
(lldb) file a.out
Current executable set to 'a.out' (x86_64).
(lldb) breakpoint set -n c
Breakpoint created: 1: name = 'c', locations = 1
(lldb) script import sys, os
(lldb) script sys.path.append(os.path.join(os.getcwd(), os.pardir))
(lldb) script import conditional_break
(lldb) breakpoint command add -p 1 "conditional_break.stop_if_called_from_a()"
(lldb) run
run
Launching '/Volumes/data/lldb/svn/trunk/test/conditional_break/a.out'  (x86_64)
(lldb) Checking call frames...
Stack trace for thread id=0x2e03 name=None queue=com.apple.main-thread:
  frame #0: a.out`c at main.c:39
  frame #1: a.out`b at main.c:34
  frame #2: a.out`a at main.c:25
  frame #3: a.out`main at main.c:44
  frame #4: a.out`start
c called from b
Continuing...
Checking call frames...
Stack trace for thread id=0x2e03 name=None queue=com.apple.main-thread:
  frame #0: a.out`c at main.c:39
  frame #1: a.out`b at main.c:34
  frame #2: a.out`main at main.c:47
  frame #3: a.out`start
c called from b
Continuing...
Checking call frames...
Stack trace for thread id=0x2e03 name=None queue=com.apple.main-thread:
  frame #0: a.out`c at main.c:39
  frame #1: a.out`a at main.c:27
  frame #2: a.out`main at main.c:50
  frame #3: a.out`start
c called from a
Stopped at c() with immediate caller as a().
a(1) returns 4
b(2) returns 5
Process 20420 Stopped
* thread #1: tid = 0x2e03, 0x0000000100000de8 a.out`c + 7 at main.c:39, stop reason = breakpoint 1.1, queue = com.apple.main-thread
  36   	
  37   	int c(int val)
  38   	{
  39 ->	    return val + 3;
  40   	}
  41   	
  42   	int main (int argc, char const *argv[])
(lldb) bt
bt
thread #1: tid = 0x2e03, stop reason = breakpoint 1.1, queue = com.apple.main-thread
  frame #0: 0x0000000100000de8 a.out`c + 7 at main.c:39
  frame #1: 0x0000000100000dbc a.out`a + 44 at main.c:27
  frame #2: 0x0000000100000e4b a.out`main + 91 at main.c:50
  frame #3: 0x0000000100000d88 a.out`start + 52
(lldb) c
c
Resuming process 20420
Process 20420 Exited
a(3) returns 6
(lldb) 

llvm-svn: 113596