renamed a bunch of identifiers to prevent future clashes

Rev: src/builtin_functions.h:1.12
Rev: src/error.h:1.40
Rev: src/errors.h:1.8
Rev: src/interpret.h:1.36
Rev: src/interpreter.h:1.33
Rev: src/object.h:1.37
Rev: src/preprocessor.h:1.19
Rev: src/security.h:1.9
Rev: src/threads.h:1.73