Use the WasmRuntime's signature list rather than keeping a separate list.

This way, if the runtime modifies the signature, such as to add special
arguments, they are reflected in the resulting function defintions.

lib/wasm/src/sections_translator.rs

@@ -27,8 +27,7 @@ pub enum SectionParsingError {
 pub fn parse_function_signatures(
     parser: &mut Parser,
     runtime: &mut WasmRuntime,
-) -> Result<Vec<Signature>, SectionParsingError> {
-    let mut signatures: Vec<Signature> = Vec::new();
+) -> Result<(), SectionParsingError> {
     loop {
         match *parser.read() {
             ParserState::EndSection => break,
@@ -51,12 +50,11 @@ pub fn parse_function_signatures(
                     ArgumentType::new(cret_arg)
                 }));
                 runtime.declare_signature(&sig);
-                signatures.push(sig);
             }
             ref s => return Err(SectionParsingError::WrongSectionContent(format!("{:?}", s))),
         }
     }
-    Ok(signatures)
+    Ok(())
 }
 
 /// Retrieves the imports from the imports section of the binary.