Use std:: on symbols declared in C++-style C headers.

src/mips/codegen-mips.cc

Index: src/mips/codegen-mips.cc
diff --git a/src/mips/codegen-mips.cc b/src/mips/codegen-mips.cc
index 0dd42d6b43e9344bd16f23c0635c3ee7c8143f8a..ff5658a190f3cedf76b7f3322171e8df373cb9cf 100644
--- a/src/mips/codegen-mips.cc
+++ b/src/mips/codegen-mips.cc
@@ -50,10 +50,10 @@ double fast_exp_simulator(double x) {
 
 
 UnaryMathFunction CreateExpFunction() {
-  if (!FLAG_fast_math) return &exp;
+  if (!FLAG_fast_math) return &std::exp;
   size_t actual_size;
   byte* buffer = static_cast<byte*>(OS::Allocate(1 * KB, &actual_size, true));
-  if (buffer == NULL) return &exp;
+  if (buffer == NULL) return &std::exp;
   ExternalReference::InitializeMathExpData();
 
   MacroAssembler masm(NULL, buffer, static_cast<int>(actual_size));