[test] Add Android (and FreeBSD) to OS checks

Add Android to the OS checks used to determine whether to import Glibc.
These tests would pass on Android were it not for the fact that Android is not
included in the Glibc check.

Also add FreeBSD where missing.

Author: modocache

test/1_stdlib/PrintFloat.swift

@@ -6,7 +6,7 @@
 // REQUIRES: executable_test
 
 import StdlibUnittest
-#if os(Linux) || os(FreeBSD)
+#if os(Linux) || os(FreeBSD) || os(Android)
   import Glibc
 #else
   import Darwin

test/Prototypes/FloatingPoint.swift

@@ -27,7 +27,7 @@ extension UInt32 : FloatingPointRepresentation {
 //  Ewwww? <rdar://problem/20060017>
 #if os(OSX) || os(iOS) || os(watchOS) || os(tvOS)
   import Darwin
-#elseif os(Linux)
+#elseif os(Linux) || os(FreeBSD) || os(Android)
   import Glibc
 #endif
 

validation-test/StdlibUnittest/Stdin.swift

@@ -6,7 +6,7 @@ import StdlibUnittest
 
 #if os(OSX) || os(iOS) || os(tvOS) || os(watchOS)
 import Darwin
-#elseif os(Linux)
+#elseif os(Linux) || os(FreeBSD) || os(Android)
 import Glibc
 #endif
 

validation-test/stdlib/String.swift

@@ -919,7 +919,7 @@ StringTests.test(
 #endif
 }
 
-#if os(Linux)
+#if os(Linux) || os(FreeBSD) || os(Android)
 import Glibc
 #endif