<rdar://problem/13021266>

Adding FindFirstGlobalVariable to SBModule and SBTarget
These calls work like FindGlobalVariables but they only return the first match found and so they can return an SBValue instead of an SBValueList for added convenience of use



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@172636 91177308-0d34-0410-b5e6-96231b3b80d8