Patch `36a2a185` introduced `wsrep_server_incoming_address()` in `10.4`.
Since AIX `/usr/include/netinet/ip.h` header defines `ip_len` as `ip_ff.ip_flen`
and `size_t const ip_len` is preprocessed as `size_t const ip_ff.ip_vhltl.ip_x.ip_xlen`,
to prevent the define from overwriting code in MariaDB,
rename the variable name to `ip_len_mdb`.

This patch is done by Tony Reix <tony.reix@atos.net>.
This patch was submitted under MCA.
Closes #1307