Move library crates under 'lib/'.

Give these crates each a more standard directory layout with sources in
a 'src' sub-sirectory and Cargo.toml in the top lib/foo directory.

Add license and description fields to each.

The build script for the cretonne crate now lives in
'lib/cretonne/build.rs' separating it from the normal library sources
under 'lib/cretonne/src'.

lib/cretonne/src/ir/builder.rs

@@ -0,0 +1,55 @@
+//! Cretonne instruction builder.
+//!
+//! A `Builder` provides a convenient interface for inserting instructions into a Cretonne
+//! function. Many of its methods are generated from the meta language instruction definitions.
+
+use ir::{types, instructions};
+use ir::{InstructionData, DataFlowGraph, Cursor};
+use ir::{Opcode, Type, Inst, Value, Ebb, JumpTable, VariableArgs, FuncRef};
+use ir::immediates::{Imm64, Uimm8, Ieee32, Ieee64, ImmVector};
+use ir::condcodes::{IntCC, FloatCC};
+
+/// Instruction builder.
+///
+/// A `Builder` holds mutable references to a data flow graph and a layout cursor. It provides
+/// convenience method for creating and inserting instructions at the current cursor position.
+pub struct Builder<'a> {
+    pub dfg: &'a mut DataFlowGraph,
+    pub pos: &'a mut Cursor<'a>,
+}
+
+impl<'a> Builder<'a> {
+    /// Create a new builder which inserts instructions at `pos`.
+    /// The `dfg` and `pos.layout` references should be from the same `Function`.
+    pub fn new(dfg: &'a mut DataFlowGraph, pos: &'a mut Cursor<'a>) -> Builder<'a> {
+        Builder {
+            dfg: dfg,
+            pos: pos,
+        }
+    }
+
+    /// Create and insert an EBB. Further instructions will be inserted into the new EBB.
+    pub fn ebb(&mut self) -> Ebb {
+        let ebb = self.dfg.make_ebb();
+        self.insert_ebb(ebb);
+        ebb
+    }
+
+    /// Insert an existing EBB at the current position. Further instructions will be inserted into
+    /// the new EBB.
+    pub fn insert_ebb(&mut self, ebb: Ebb) {
+        self.pos.insert_ebb(ebb);
+    }
+
+    // Create and insert an instruction.
+    // This method is used by the generated format-specific methods.
+    fn insert_inst(&mut self, data: InstructionData) -> Inst {
+        let inst = self.dfg.make_inst(data);
+        self.pos.insert_inst(inst);
+        inst
+    }
+}
+
+// Include code generated by `meta/gen_instr.py`. This file includes `Builder` methods per
+// instruction format and per opcode for inserting instructions.
+include!(concat!(env!("OUT_DIR"), "/builder.rs"));