Implementation of basic data flow analysis for PowerPC (#212)

* WIP implementation

* * Move flow analysis to dedicated file
* Show string constants inline
* Handle calls to MWCC "sled" helpers which otherwise disrupt flow analysis

* Run cargo insta review

* Apply clippy feedback

* Update more tests.

* Remove std use from ppc flow analysis

* Try to make wasm build work again

* More test changes

* Probably last wasm fix

* Formatting

* Fix WASM

* One more clippy thing

* Fixed display of float constants in a LFS or LFD instruction in case where there is a branch to the subsequent instruction with a different register value.

* On lines with a reloc, only hide Symbol type data flow values rather than all data flow values.

* Formatting

objdiff-wasm/src/api.rs

@@ -401,6 +401,7 @@ impl From<diff::display::DiffTextColor> for DiffTextColor {
             diff::display::DiffTextColor::Replace => DiffTextColor::Replace,
             diff::display::DiffTextColor::Delete => DiffTextColor::Delete,
             diff::display::DiffTextColor::Insert => DiffTextColor::Insert,
+            diff::display::DiffTextColor::DataFlow => DiffTextColor::DataFlow,
             diff::display::DiffTextColor::Rotating(v) => DiffTextColor::Rotating(v),
         }
     }