Merge pull request #498 from savi-lang/fix/trace-data-mutable-bool

Fix tracing of `Bool` in `TraceData.Mutable`.

Merge pull request #497 from savi-lang/fix/some-error-messages

Fix some compiler errors to show more information.

Merge pull request #494 from savi-lang/add/indexable-stuff

Improvements to `Indexable` trait

Merge pull request #493 from savi-lang/add/reflection-into-string

Update `ReflectionOfType` to implement `IntoString` trait.

Merge pull request #491 from savi-lang/add/prefer-static-link

Add `:prefer static` option for `:ffi_link_lib`.

Merge pull request #490 from savi-lang/add/library-path-env

Add support for LIBRARY_PATH environment variable.

Merge pull request #488 from savi-lang/fix/struct-field-cast

Fix for FFI casting a struct to its pointer field.

Merge pull request #483 from savi-lang/add/ffi-global-cpointer

Add `:ffi global cpointer` declarator to give the address of a C global.

Merge pull request #482 from savi-lang/add/ffi-globals

Add `:ffi global` variable bindings.

Merge pull request #481 from savi-lang/add/env-out-flush

Call `pony_os_stdout_setup` at the start of a Savi program.