Add some basic sanity checks to DynamicLoaderDarwinKernel::ReadKextSummaryHeader()
when it is reading the kext table, in case we're reading out of a core file with
corrupt contents in this region.
<rdar://problem/16601915> 


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@206233 91177308-0d34-0410-b5e6-96231b3b80d8