Add encoding size information to EncInfo.

Two new pieces of information are available for all encoding recipes:

- The size in bytes of an encoded instruction, and
- The range of a branch encoded with the recipe, if any.

In the meta language, EncRecipe takes two new constructor arguments. The
size is required for all encodings and branch_range is required for all
recipes used to encode branches.

lib/cretonne/src/isa/intel/enc_tables.rs

@@ -5,5 +5,6 @@ use ir::types;
 use isa::EncInfo;
 use isa::constraints::*;
 use isa::enc_tables::{Level1Entry, Level2Entry};
+use isa::encoding::RecipeSizing;
 
 include!(concat!(env!("OUT_DIR"), "/encoding-intel.rs"));