Add IsConstant to Global

llvm/global.go

@@ -14,6 +14,12 @@ type Global struct {
 	// TODO complete this
 }
 
+func (this *Global) IsConstant () {
+	// FIXME globals are not always constant... perhaps there is a better
+	// way of doing this? maybe making a separate type ConstGlobal that
+	// embeds Global? would have to do away with Constant member.
+}
+
 func (this *Global) Type () Type {
 	return &TypePointer {
 		AddressSpace: this.AddressSpace,