Change the mechanism around SBValue::GetSP() so that it always requires the target API lock AND the
process StopLocker (if there is a process) before it will hand out SBValues.  We were doing this in 
an ad hoc fashion previously, and then playing whack-a-mole whenever we found a place where we should
have been doing this but weren't.  Really, it doesn't make sense to be poking at SBValues when the target
is running, the dynamic and synthetic values can't really be computed, and the underlying memory may be
incoherent.

<rdar://problem/13819378> Sometimes when stepping fast, my inferior is killed by debugserver


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@181863 91177308-0d34-0410-b5e6-96231b3b80d8
<rdar://problem/13883385>

Python breakpoint actions can return False to say that they don't want to stop at the breakpoint to which they are associated
Almost all of the work to support this notion of a breakpoint callback was in place, but two small moving parts were missing:
a) the SWIG wrapper was not checking the return value of the script
b) when passing a Python function by name, the call statement was dropping the return value of the function
This checkin addresses both concerns and makes this work
Care has been taken that you only keep running when an actual value of False has been returned, and that any other value (None included) means Stop!



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@181866 91177308-0d34-0410-b5e6-96231b3b80d8