[getdns-api] Distinguish strings from wire format in conversion functions

[Willem Toorop]

Since the library used "Standard Integer Types" anyway, why not use it
in the conversion function prototypes (from 4.2) to distinguish strings
from wire format names:

char *getdns_convert_dns_name_to_fqdn(const uint8_t *dns_name_wire_fmt);
uint8_t *getdns_convert_fqdn_to_dns_name(const char *fqdn_as_string);

What do you think?