Buffer overflow in liboggz, httpdate.c, function httpdate_parse

The function httpdate_parse writes 4 bytes to the three byte variables wday and month. These are supposed to store a 3 byte string, however that misses that the string needs a null terminating byte. Making the variables 4 bytes fixes this. Also the parser string should limit the size of the month string. See attached patch.

This bug was found with the help of address sanitizer. Can be reproduced by compiling liboggz with -fsanitize=address in CFLAGS+LDFLAGS and running make check.