Document FIXED_POINTS_NO_RANDOM

README.md

@@ -33,6 +33,7 @@ This means:
 These are symbols you can define prior to library inclusion to alter the behaviour of the library.
 
 - `FIXED_POINTS_USE_NAMESPACE`: Define this to wrap all classes and functions in the namespace `FixedPoints`. Useful for preventing naming conflicts.
+- `FIXED_POINTS_NO_RANDOM`: Define this to disable the random utility functions. Useful for systems that don't have access to `long random(void)` from avr-libc.
 
 ## Contents
 This library supplies two core types and sixteen type aliases.