Removefile returns remove() and CreateFolder returns fs_makedir(),
but they returns 0 on success and non-zero on error. Fix that,
RemoveFile and CreateFolder should return true on success.
(they return false when the type argument is invalid).
note: bug has remained unoticed because noone uses CreateFolder, and the
user of RemoveFile (the demo browser's remove button) doesn't
check the return value.