Changed checkprefix() to use it and those instances of strnequal() that
compare host names or other protocol strings that are defined to be
independent of case in the C locale. This should fix a few more
Turkish locale problems.
(http://curl.haxx.se/bug/view.cgi?id=2154627) which pointed out that libcurl
uses strcasecmp() in multiple places where it causes failures when the
Turkish locale is used. This is because 'i' and 'I' isn't the same letter so
strcasecmp() on those letters are different in Turkish than in English (or
just about all other languages). I thus introduced a totally new internal
function in libcurl (called Curl_ascii_equal) for doing case insentive
comparisons for english-(ascii?) style strings that thus will make "file"
and "FILE" match even if the Turkish locale is selected.
configure. An attempt to fix warnings when we build and the strlcat() function
is provided by one if the libs (gss or krb4) since then we have no protos
for it in a system header.
