add flatbuffers

commit 6da1cf79d90eb242e7da5318241d42279a3df3ba
Author: Max Burke <max@urbanlogiq.com>
Date:   Sun Jan 19 14:47:28 2020 -0800

    [rust] Add use declarations to Rust-generated bindings for imported FB definitions (#5645)

    * Bugfix for Rust generation of union fields named with language keywords

flatbuffers/swift/Sources/FlatBuffers/Int+extension.swift

@@ -0,0 +1,31 @@
+import Foundation
+
+extension Int {
+    
+    /// Moves the current int into the nearest power of two
+    ///
+    /// This is used since the UnsafeMutableRawPointer will face issues when writing/reading
+    /// if the buffer alignment exceeds that actual size of the buffer
+    var convertToPowerofTwo: Int {
+        guard self > 0 else { return 1 }
+        var n = UOffset(self)
+        
+        #if arch(arm) || arch(i386)
+        let max = UInt32(Int.max)
+        #else
+        let max = UInt32.max
+        #endif
+        
+        n -= 1
+        n |= n >> 1
+        n |= n >> 2
+        n |= n >> 4
+        n |= n >> 8
+        n |= n >> 16
+        if n != max {
+            n += 1
+        }
+
+        return Int(n)
+    }
+}