Added sqrt and pow for arm and x64 - to fix build failures.

src/mips/codegen-mips.cc

Index: src/mips/codegen-mips.cc
===================================================================
--- src/mips/codegen-mips.cc	(revision 4053)
+++ src/mips/codegen-mips.cc	(working copy)
@@ -292,11 +292,16 @@
 }
 
 
-void CodeGenerator::GeneratePow(ZoneList<Expression*>* args) {
+void CodeGenerator::GenerateMathPow(ZoneList<Expression*>* args) {
   UNIMPLEMENTED_MIPS();
 }
 
 
+void CodeGenerator::GenerateMathSqrt(ZoneList<Expression*>* args) {
+  UNIMPLEMENTED_MIPS();
+}
+
+
 // This should generate code that performs a charCodeAt() call or returns
 // undefined in order to trigger the slow case, Runtime_StringCharCodeAt.
 // It is not yet implemented on ARM, so it always goes to the slow case.