[asan] Introduce new approach for ODR violation detection based on odr indicator symbols.

This is a compiler-rt part of this http://reviews.llvm.org/D15642 patch. Here,
we add a new approach for ODR violation detection.
Instead of using __asan_region_is_poisoned(g->beg, g->size_with_redzone) on
global address (that would return false now due to using private alias), we can
use new globally visible indicator symbol to perform the check.

Differential Revision: http://reviews.llvm.org/D15644

llvm-svn: 260076