Bump base lower version to 4.5 (the version GHC 7.4.1 came with)

System/Posix.hs

System/Posix/ByteString.hs

System/Posix/ByteString/FilePath.hsc

System/Posix/Directory.hsc

System/Posix/Directory/ByteString.hsc

System/Posix/Directory/Common.hsc

System/Posix/DynamicLinker.hsc

System/Posix/DynamicLinker/ByteString.hsc

System/Posix/DynamicLinker/Common.hsc

System/Posix/DynamicLinker/Module.hsc

System/Posix/DynamicLinker/Module/ByteString.hsc

System/Posix/DynamicLinker/Prim.hsc

System/Posix/Env.hsc

System/Posix/Env/ByteString.hsc

System/Posix/Error.hs

System/Posix/Files.hsc

System/Posix/Files/ByteString.hsc

System/Posix/Files/Common.hsc

System/Posix/IO.hsc

System/Posix/IO/ByteString.hsc