ocaml: phase 6 Float module: sqrt/sin/cos/pow/floor/ceil/round/pi (+6 tests, 378 total)

Wraps host SX math primitives via _float_* builtins. Float.pi is a
Float literal in the OCaml-side module.

lib/ocaml/runtime.sx

@@ -316,6 +316,14 @@
 
    module Float = struct
      let to_string f = _string_of_float f
+     let sqrt f = _float_sqrt f
+     let sin f = _float_sin f
+     let cos f = _float_cos f
+     let pow a b = _float_pow a b
+     let floor f = _float_floor f
+     let ceil f = _float_ceil f
+     let round f = _float_round f
+     let pi = 3.141592653589793
    end ;;
 
    module Printf = struct