bug#14743: 24.3.50; doc string of `read-regexp'

[Drew Adams]

The PROMPT description is also not quite correct.

Suggestion:

"Read and return a regular expression as a string.
If PROMPT does not end with a colon and possibly whitespace then
append \": \" to it.

Optional argument DEFAULT is a string or a list of the form
\(DEFLT . SUGGESTIONS), where DEFLT is a string or nil.

The string DEFAULT or DEFLT is added to the prompt and is returned as
the default value if the user enters empty input.  The empty string is
returned if DEFAULT or DEFLT is nil and the user enters empty input.

SUGGESTIONS is a list of strings that can be inserted into the
minibuffer using `\\<minibuffer-local-map>\\[next-history-element]'.  The 
values supplied in SUGGESTIONS are
prepended to the list of standard suggestions, which include the tag
at point, the last isearch regexp, the last isearch string, and the
last replacement regexp.

Optional argument HISTORY is a symbol to use for the history list.
If nil then use `regexp-history'."