Fix crashes in untested VA features

[pascalkuthe]

• Add tests for analog initial statements.
• Generate lint for ports without direction (see #40).
• Improve lint messages.
• Allow parameter declarations without explicit type (fixes #46).
• Fix some errors causing a panic during type inference.
• Fix outdated issue link.
• Fix crash when for %r format specifier.

[pascalkuthe]

bors merge

[bors[bot]]

Build failed:

• ci

[pascalkuthe]

bors merge

[bors[bot]]

Build succeeded:

• ci