LEB128-encode addresses in data section

asm.js

@@ -984,7 +984,7 @@ export class Assembler {
             return [
                 ...(loc.mem == 0 ? [ 0 ] : [ 2, loc.mem ]),
                 opcodes["i32.const"],
-                loc.addr,
+                ...this.leb128(loc.addr),
                 opcodes["end"],
                 data.length,
                 ...data,