[analyzer] Teach the analyzer about implicit initialization of statics

[analyzer] Teach the analyzer about implicit initialization of statics
in ObjCMethods.

Extend FunctionTextRegion to represent ObjC methods as well as
functions. Note, it is not clear what type ObjCMethod region should
return. Since the type of the FunctionText region is not currently used,
defer solving this issue.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164046 91177308-0d34-0410-b5e6-96231b3b80d8