Converting IP addresses to strings

When debugging, it is highly desirable to be able to print IP addresses in the common IPv4 and IPv6 ``human readable'' formats. Olsrd provides some functions for conversion of the olsr_ip_addr data-type to a NULL terminated char array. The most used of these functions is defined in olsr.h as:

char *
olsr_ip_to_string(union olsr_ip_addr *);

Since this function uses the olsr_ip_addr union, it is IP version transparent. This function uses a static allocated buffer, so it is not reentrant. That means that it should not be used twice in the same function call.