Motivation / Problem

The assert_compile macro is now just an alias for static_assert. Moreover, C++17 static_assert gains a single argument variant, so we don't have to stringify the expression ourselves.

Description

A whole lot of changes to just remove 2 lines of code :)

Limitations

Doesn't use any feature macros to check whether the compiler actually supports the single argument static_assert variant, but we're assuming a C++17 compliant compiler at this point anyway.

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • PR must be added to API tracker