Add no_function feature to disable script-defined functions.

Cargo.toml

@@ -18,16 +18,18 @@ include = [
 num-traits = "*"
 
 [features]
-#default = ["no_index", "no_float", "only_i32", "no_stdlib", "unchecked"]
+#default = ["no_function", "no_index", "no_float", "only_i32", "no_stdlib", "unchecked"]
 default = []
-debug_msgs = []
-unchecked = []
-no_stdlib = []
-no_index = []
-no_float = []
-only_i32 = []
-only_i64 = []
+debug_msgs = []     # print debug messages on function registrations and calls
+unchecked = []      # unchecked arithmetic
+no_stdlib = []      # no standard library of utility functions
+no_index = []       # no arrays and indexing
+no_float = []       # no floating-point
+no_function = []    # no script-defined functions
+only_i32 = []       # set INT=i32 (useful for 32-bit systems)
+only_i64 = []       # set INT=i64 (default) and disable support for all other integer types
 
 [profile.release]
 lto = "fat"
 codegen-units = 1
+#opt-level = "z"     # optimize for size