moved crates in lib/ to src/, renamed crates, modified some files' text (#660)

moved crates in lib/ to src/, renamed crates, modified some files' text (#660)

cranelift/codegen/meta/src/lib.rs

@@ -0,0 +1,13 @@
+#[macro_use]
+mod cdsl;
+
+pub mod error;
+pub mod gen_registers;
+pub mod gen_settings;
+pub mod gen_types;
+pub mod isa;
+
+mod base;
+mod constant_hash;
+mod srcgen;
+mod unique_table;