At the moment tsdb cannot be built on Illumos/Solaris due to
- An exclude tag against Solaris is added in db_unix.go
- We use built-in syscall package, which doesn't have nmmap and munmap support
This PR supports build on Illumos/Solaris by remove the Solaris exclude tag in db_unix.go
At the same time use golang.org/x/sys/unix package instead of syscall package, since it has Solaris nmmap and munmap implementation.
Jingkai He
Fabian Reinartz