Errata for SRFI 48: Intermediate Format Strings

Incorrect mutation of literal list in example

errata-1: See Sudarshan S Chawathe's comment in the email archives.

Incorrect formatting by reference implementation

errata-2: See the thread started by Donald Allen about several bugs he discovered in the reference implementation. Some have been fixed directly in the SRFI document, but others remain.

errata-3: Hamayama fixed the bugs and added tests as well.

errata-4: Hamayama fixed another bug and added tests for Racket and Sagittarius, too.

errata-5: Hamayama accounted for exponential notation.

errata-6: Hamayama accounted for infinities, NANs, "1.", etc.

errata-7: Hamayama adjusted for Gambit; updated tests; refactored the test tool; added tests for MIT/GNU Scheme, Chez Scheme, and Chicken Scheme; fixed tests for R6RS's 'error' procedure and for Racket, and removed an unnecessary procedure.