Codechange: Add base() method to StrongType to allow access to the base type without casting. (#11445)

This removes the ability to explicitly cast to the base type, but the requirement
to use .base() means the conversion is still explicit.

Cleanup: Remove some unused functions. (#11429)

These were picked up with cppcheck.

Revert 8fa61533: "Fix 30ae072: when a road type is hidden, towns may not build them even when that flag is set"

This reverts commit 8fa61533f041b16497282107afa600e919ba7154.

Fix: commands with a RoadType in their arguments were not validated properly (#9944)

Although it was checked that RoadType was not 63 (INVALID_ROADTYPE),
and all values lower than 63 are fine, it also allowed values higher
than 63. As the RoadType is a "byte", it could contain values up
to 255.

(svn r15077) -Codechange: enumify DAYS_IN_YEAR and DAYS_IN_LEAP_YEAR
-Change: when computing daily running cost, divide by 365 (instead of 364). Since r12134, the rounding errors don't need this correction anymore