OperatingSystem plug-ins need to avoid running code when fetching thread...

OperatingSystem plug-ins need to avoid running code when fetching thread lists. This patch helps with that by making all SBValue objects that are fetched not try to do dynamic type resolution. Objective C can end up running code to fetch a list of all ISA pointers so we can tell when something is dynamic and this running code could cause the OS plug-in to continue the target.

This fix disabled dynamic types, fetches the new threads from the OS plug-in, then restores the setting.

<rdar://problem/20768407> 

llvm-svn: 237465