[analyzer] Fix memory space of static locals seen from nested blocks.

When a block within a function accesses a function's static local variable,
this local is captured by reference rather than copied to the heap.

Therefore this variable's memory space is known: StaticGlobalSpaceRegion.
Used to be UnknownSpaceRegion, same as for stack locals.

Fixes a false positive in MacOSXAPIChecker.

rdar://problem/30105546
Differential revision: https://reviews.llvm.org/D28946

llvm-svn: 292800