[PATCH] [sanitizer] Support sandboxing in sanitizer coverage.

[Kostya Serebryany]

Looks reasonable, but I'd like to see a lit test :)

================
Comment at: lib/sanitizer_common/sanitizer_coverage.cc:90
@@ +89,3 @@
+  unsigned module_name_length = internal_strlen(module);
+  CovHeader header;
+  header.pid = pid;
----------------
use C++ initializer:

http://reviews.llvm.org/D3726