Drop some patches for old LibreSSL versions.

The ports tree currently has LibreSSL 2.7.3, so remove some patches added to
support LibreSSL < 2.5 (also, according to brnrd@, they are currently broken).
Cleaning up our existing patches also helps us move to Qt 5.10.

Reviewed by: tcberner
Differential Revision: https://reviews.freebsd.org/D15338