[PATCH] [MC] report error instead of assertion for non-zero initializer in .bss section

[Rafael Ávila de Espíndola]

LGTM with a nit.

================
Comment at: lib/MC/MCAssembler.cpp:787
@@ +786,3 @@
+          if (DF.getContents()[i]) {
+            if (auto ELFSec = dyn_cast<const MCSectionELF>(&SD->getSection()))
+              report_fatal_error("non-zero initializer found in section '" +
----------------
nit:

use 'auto *' to make it clear that it is a pointer.

http://reviews.llvm.org/D4199