closes#1414
std.io.InStream.read now can return less than buffer size
introduce std.io.InStream.readFull for previous behavior
add std.os.File.openWriteNoClobberC
rename std.os.deleteFileWindows to std.os.deleteFileW
remove std.os.deleteFilePosix
add std.os.deleteFileC
std.os.copyFile no longer takes an allocator
std.os.copyFileMode no longer takes an allocator
std.os.AtomicFile no longer takes an allocator
add std.os.renameW
add windows support for std.os.renameC
add a test for std.os.AtomicFile