package/znc: bump version to 1.7.0

Increased minimum gcc version to 4.8 as mentioned in the Changelog:
https://wiki.znc.in/ChangeLog/1.7.0

Removed all patches:
- 0001 was applied upstream:
https://github.com/znc/znc/commit/483074cbf82a48a3ff01838fcbaec00553d1882c

- 0002 is not needed anymore after upstream switched Csocket to a git
  submodule:
https://github.com/znc/znc/commit/9166e6ed40f0c7a85eee0d024b12510c13863f55#diff-8a725997e024d92d67b33a90cffb8342



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>