net-misc/directvnc: prune 0.7.5 version

Signed-off-by: Dennis Lan <dennis.yxun@gmail.com>
net-misc/directvnc: rework 0.7.6 version

1) bump to EAPI 5
2) enable mouse by defalt
3) adjust src_*

Signed-off-by: Dennis Lan <dennis.yxun@gmail.com>