Add missing std:: prefixes to some calls. C++ doesn't require that <cfoo>
headers provide symbols outside namespace std and the LLVM coding standards
state that we should prefix all of them.

llvm-svn: 122192
diff --git a/llvm/lib/Target/SubtargetFeature.cpp b/llvm/lib/Target/SubtargetFeature.cpp
index b35190a..ba53d63 100644
--- a/llvm/lib/Target/SubtargetFeature.cpp
+++ b/llvm/lib/Target/SubtargetFeature.cpp
@@ -162,7 +162,7 @@
   
   errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
        << "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
-  exit(1);
+  std::exit(1);
 }
 
 //===----------------------------------------------------------------------===//