package/tig: bump version to 2.5.12
For change log since 2.5.10, see:
https://github.com/jonas/tig/releases/tag/tig-2.5.11
https://github.com/jonas/tig/releases/tag/tig-2.5.12
The autoconf configure script of this new version (generated with
autoconf 2.72) now requires pkg-config. Therefore, this commit also
adds host-pkgconf in _DEPENDENCIES.
Signed-off-by: Julien Olivain <ju.o@free.fr>