First baby steps to supporting memory accesses

Currently we don't actually sandbox the memory at all, so you can do evil things
like read and write the host's memory. We also don't support growing memory or
cranelift-compatible ABI that passes the memory offset as an argument.

We also always immediately allocate the buffer when encountering a memory section,
there is preliminary support for translating a buffer which can then have the real
offset replaced using relocations (and returning a different type when doing so)
but I haven't written the code that actually does relocation so it doesn't work yet.

src/error.rs

@@ -20,6 +20,12 @@ impl From<BinaryReaderError> for Error {
     }
 }
 
+impl From<!> for Error {
+    fn from(other: !) -> Self {
+        other
+    }
+}
+
 impl From<capstone::Error> for Error {
     fn from(e: capstone::Error) -> Self {
         Error::Disassembler(e.to_string())