Add unconvert linter

This linter checks for unnecessary type convertions.

Some convertions are whitelisted because their type is different
on 32bit platforms

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

sys/stat_unix.go

@@ -4,6 +4,7 @@ package sys
 
 import (
 	"syscall"
+	"time"
 )
 
 // StatAtime returns the Atim
@@ -20,3 +21,8 @@ func StatCtime(st *syscall.Stat_t) syscall.Timespec {
 func StatMtime(st *syscall.Stat_t) syscall.Timespec {
 	return st.Mtim
 }
+
+// StatATimeAsTime returns st.Atim as a time.Time
+func StatATimeAsTime(st *syscall.Stat_t) time.Time {
+	return time.Unix(st.Atim.Sec, st.Atim.Nsec)
+}