Fixed SF.net bug #3571331, check_http converts semicolon to newline in -k

This commit fixes sourceforge.net bug id 3571331.
The semicolon was defined as input delimiter for multiple values in the -k arguments.
Due to the fact the semicolon is a valid character for HTTP header fields this input delimiter function was removed.
It is still possible to pass multiple header fields via multiple -k (like described in helptext).