* Fix signed and unsigned arguments not being considered equal when highlighting

* Remove unused Eq derive

The flagset .contains check doesn't work like this.

Fixes #199

We have specific diff logic that relies on knowing
which object is the target object, and which is the
base. generate_mapping_symbols was designed in such
a way that it would reverse the target/base, leading
to a match percent shown that's different when it
gets applied.

Fixes #200

COFF objects in particular don't contain the size of
symbols. We infer the size of these symbols by
extending them to the next symbol. If a tool emits
symbols for branch targets, this causes the inferred
size to be too small.

This checks if a symbol starts with a certain prefix
(right now, just .L or LAB_), and skips over it
during symbol size inference.

Resolves #174

When searching for a symbol by name, only look at
symbols that are defined within the object,
ignoring extern symbols (symbols without section).

Fixes #180
Fixes #181