S9 LIB  (string-find string1 string2)     ==>  offset | #f
        (string-ci-find string1 string2)  ==>  offset | #f

Attempt to find the pattern STRING1 in the text STRING2. Return
the offset of the first occurrence of STRING1 in STRING2 or #F,
if STRING2 does not contain STRING1. STRING-CI-FIND does the same,
but ignores case.

This program is based on "A Very Fast Substring Search Algorithm",
Daniel M. Sunday, CACM v33, #8, August 1990 and the
SUBSTRING-SEARCH-MAKER procedure by Ken Dickey (1990).

(string-find "test" "This is a test string")     ==>  10
(string-find "TEST" "This is a test string")     ==>  #f
(string-ci-find "TEST" "This is a test string")  ==>  10
