Update inet_aton.c from FreeBSD uptream removes advertising clause

[michaelortmann]

Found by: michaelortmann
Patch by: michaelortmann
Fixes:

One-line summary:
The new https://github.com/freebsd/freebsd/blob/455de2f90f71a495eb5068b060c17de9bfcffda6/lib/libc/inet/inet_addr.c removes advertising clause from license.

Additional description (if needed):
The only user of inet_aton() within eggdrop is one function in dns module. I tested this function and enhanced its logging. But you cant see the DNS: Valid dns-server message, because #948 is not merged yet. egg_inet_aton() now uses isdigit(), islower(), isspace() instead of egg_*() due to all of them being posix 2001.
Removal of the advertising clause helps with #226 see #226 (comment)_

Test cases demonstrating functionality (if applicable):

$ grep INET_ATON config.h
#define HAVE_INET_ATON 1
$ nm eggdrop|grep aton
                 U inet_aton@@GLIBC_2.2.5

$ grep INET_ATON config.h
/* #define HAVE_INET_ATON 1 */
$ nm eggdrop|grep aton
00000000000589c0 T egg_inet_aton

[vanosg]

Please test the cases that are affected by these changes and show code equivalency

[vanosg]

This is more than just removing the advertisement, there are some semi-significant updates to the code being run. This would require some extensive testing to validate- please provide test cases for the new code in use. Thanks!

[michaelortmann]

vanosg: As we spoke, the multi line fix is committed and thus this PR is ready for review again.