Enabling LLVM 5.0 and making fixes to track changes in LLVM for the past

couple months.
The changes are tested with LLVM 3.9, 4.0 and trunk on MacOS (sse4,
avx2, skx).

llvmutil.h

@@ -51,7 +51,11 @@
   #include <llvm/IR/Constants.h>
 #endif
 
+#if ISPC_LLVM_VERSION <= ISPC_LLVM_3_9
 #define PTYPE(p) (llvm::cast<llvm::SequentialType>((p)->getType()->getScalarType())->getElementType())
+#else // LLVM 4.0+
+#define PTYPE(p) (llvm::cast<llvm::PointerType>((p)->getType()->getScalarType())->getElementType())
+#endif
 
 namespace llvm {
     class PHINode;