+/*
+ * Case insensitive string hashing.
+ *
+ * The lower/upper case bit is masked out (forcing all letters to be capitals).
+ * The major side effect on non-alpha characters is mapping the symbols and
+ * digits into the control character range (which should be harmless).
+ * The duplication (with respect to the hash value) of printable characters
+ * are that '`', '{', '|', '}' and '~' map to '@', '[', '\', ']' and '^'
+ * respectively (which seems tolerable).
+ *
+ * For EBCDIC, the alpha mapping is to lower case, most symbols go to control
+ * characters. The only duplication is '0' mapping to '^', which is better
+ * than for ASCII.
+ */