enums and match (in the compiler written in Finch)

enum Color { Red, Green, Blue }   enum Status { Ok = 200, NotFound = 404 }

Color.Red, Color(n) (checked), int(c), == and != only, printed by name, usable as
map keys and struct fields, with methods (fn Color.next()).

match value { Red, Green -> ... Blue -> ... else -> ... } as a statement, or as an
expression that gives a value. Works on enums, whole numbers, chars, text and bools;
a match on an enum has to handle every variant or end with else, and says which are
missing. A bare variant name (Red) is enough inside a match on an enum.

Only the self-hosted compiler has them; tests/new holds their tests, tests/run stays what
the C++ compiler also runs. boot.sh: 31 passed.

tests/new/enums.out

@@ -0,0 +1,14 @@
+Green Blue 2 418
+true false
+red blue false true
+fine odd
+Pixel(color: Blue, x: 3)
+[Red, Blue] 2
+a red one
+something else
+NotFound Ok
+medium
+2
+two!
+5 {Red: 2, Blue: 5}
+Green!