contrib/bsddialog: Import version 1.0.3

Change --mixedform output to adapt to bsdinstall restoring dialog(1)
behavior.

Avoid to print the field value to output if <fieldlen> is read-only
(less than or equal to zero). This fixes passwords in wlanconfig,
avoiding to print also SSID.

To note --mixedform continues to print field value if <flag> is
read-only. This avoids breaking netconfig and netconfig_ipv6.

See /usr/src/contrib/bsddialog/CHANGELOG '2024-05-27 Version 1.0.3'
for more detailed information.

Reported by: garga