Add call and call_indirect instructions.

Add a new IndirectCall instruction format which has a value callee as
well as the call arguments.

Define call and call_indirect instructions.

lib/cretonne/src/ir/builder.rs

@@ -5,7 +5,7 @@
 
 use ir::{types, instructions};
 use ir::{InstructionData, DataFlowGraph, Cursor};
-use ir::{Opcode, Type, Inst, Value, Ebb, JumpTable, VariableArgs, FuncRef};
+use ir::{Opcode, Type, Inst, Value, Ebb, JumpTable, VariableArgs, SigRef, FuncRef};
 use ir::immediates::{Imm64, Uimm8, Ieee32, Ieee64, ImmVector};
 use ir::condcodes::{IntCC, FloatCC};