When increasing the amount of a file read, read the total of the Mach-O header
plus the size of the load commands in case the LC_UUID load command comes near
the end of the file.
<rdar://problem/16599318> 


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@206865 91177308-0d34-0410-b5e6-96231b3b80d8