Do not use unsafe syscall when appengine constraint is set
diff --git a/termsize.go b/termsize.go
index df97e7e..1ca6a85 100644
--- a/termsize.go
+++ b/termsize.go
@@ -1,4 +1,4 @@
-// +build !windows,!plan9,!solaris
+// +build !windows,!plan9,!solaris,!appengine
 
 package flags
 
diff --git a/termsize_nosysioctl.go b/termsize_nosysioctl.go
index 2a9bbe0..3d5385b 100644
--- a/termsize_nosysioctl.go
+++ b/termsize_nosysioctl.go
@@ -1,4 +1,4 @@
-// +build windows plan9 solaris
+// +build windows plan9 solaris appengine
 
 package flags
 
diff --git a/termsize_unix.go b/tiocgwinsz_bsdish.go
similarity index 100%
rename from termsize_unix.go
rename to tiocgwinsz_bsdish.go
diff --git a/termsize_linux.go b/tiocgwinsz_linux.go
similarity index 100%
rename from termsize_linux.go
rename to tiocgwinsz_linux.go
diff --git a/termsize_other.go b/tiocgwinsz_other.go
similarity index 100%
rename from termsize_other.go
rename to tiocgwinsz_other.go