Modified the host process monitor callback function Host::StartMonitoringChildProcess

to spawn a thread for each process that is being monitored. Previously
LLDB would spawn a single thread that would wait for any child process which
isn't ok to do as a shared library (LLDB.framework on Mac OSX, or lldb.so on
linux). The old single thread used to call wait4() with a pid of -1 which 
could cause it to reap child processes that it shouldn't have.

Re-wrote the way Function blocks are handles. Previously I attempted to keep
all blocks in a single memory allocation (in a std::vector). This made the
code somewhat efficient, but hard to work with. I got rid of the old BlockList
class, and went to a straight parent with children relationship. This new 
approach will allow for partial parsing of the blocks within a function.

llvm-svn: 111706