Switch from version strings to schema versions

Should help reduce some churn a bit!

crates/wasm-bindgen-cli-support/src/lib.rs

@@ -163,7 +163,7 @@ fn extract_programs(module: &mut Module) -> Vec<shared::Program> {
                     panic!("failed to decode what looked like wasm-bindgen data: {}", e)
                 }
             };
-            if p.version != version {
+            if p.schema_version != shared::SCHEMA_VERSION {
                 panic!("
 
 it looks like the Rust project used to create this wasm file was linked against

crates/wasm-bindgen-macro/src/ast.rs

@@ -351,6 +351,7 @@ impl Program {
                     })
                 }),
                 ("version", &|a| a.str(&shared::version())),
+                ("schema_version", &|a| a.str(&shared::SCHEMA_VERSION)),
             ]);
             a.cnt
         };

crates/wasm-bindgen-shared/src/lib.rs

@@ -5,6 +5,8 @@ extern crate fnv;
 use std::char;
 use std::hash::{Hash, Hasher};
 
+pub const SCHEMA_VERSION: &str = "0";
+
 #[derive(Deserialize)]
 pub struct Program {
     pub exports: Vec<Export>,
@@ -12,6 +14,7 @@ pub struct Program {
     pub imports: Vec<Import>,
     pub custom_type_names: Vec<CustomTypeName>,
     pub version: String,
+    pub schema_version: String,
 }
 
 #[derive(Deserialize)]