Check in the wasmstandalone code.

This is based on the code in https://github.com/denismerigoux/cretonne/commits/wasm2cretonne
before wasmstandalone was removed, with minor updates for the new library structure.
It is not yet updated for the latest cretonne API changes.

filetests/globals.wast

@@ -0,0 +1,8 @@
+(module
+  (global $x (mut i32) (i32.const 4))
+  (memory 1)
+  (func $main (local i32)
+    (i32.store (i32.const 0) (get_global $x))
+  )
+  (start $main)
+)