QFtp's _q_parseUnixDir can't parse dates on leap years

This year is a leap year, which is why we found the bug this year. When we issue a QFtp::list then the QFtp::listInfo signal will not always return us QUrlInfo entries that yield true for info.lastModified().isValid().

I have attached a program where I copy-pasted the function in qftp.cpp that is responsible for the bug. I pass that function a line that can possibly come from an FTP server the 29th of February on a leap year (like this year, 2012). The function returns with a QUrlInfo where lastModified isn't valid. As illustrated in the test program.

I will attach a possible patch to fix this issue afterward.