Use default value for make-fluid in Scheme files

Use default value for make-fluid in Scheme files

* module/ice-9/boot-9.scm (%exception-handler)
  (%running-exception-handlers, read-eval?, *repl-stack*)
  (make-mutable-parameter):
* module/ice-9/getopt-long.scm (%program-name):
* module/language/elisp/runtime.scm (built-in-macro, defspecial):
* module/srfi/srfi-39.scm (make-parameter/helper):
* module/system/base/language.scm (*current-language*):
* module/system/base/message.scm (*current-warning-port*):
  (*current-warning-prefix*):
* module/system/base/target.scm (%target-type, %target-endianness)
  (%target-word-size):
* module/texinfo/plain-text.scm (*indent*, *itemizer*):
* benchmark-suite/lib.scm (prefix-fluid):
* test-suite/lib.scm (prefix-fluid): Give fluids a useful default
  value.