Renamed bigint -> inttypes / int

A lot of refactoring larger integer types. Fix a number
of casting errors, but mostly rename things. Also try to
limit use of template-like macros as they bloat the binary
if not used in moderation. We were able to reduce the size of
typed array code as well by using a single view types.

tools/amalg.janet

@@ -36,6 +36,7 @@
     "src/core/fiber.c"
     "src/core/gc.c"
     "src/core/io.c"
+    "src/core/inttypes.c"
     "src/core/marsh.c"
     "src/core/math.c"
     "src/core/os.c"