printf: renders \x as a literal but should error due to missing hexadecimal number

[jfinkels]

Steps to reproduce:

printf '\x'

What happens now: uutils printf renders this as a literal, as-is:

\x

What I expected to happen: GNU printf terminates with an error message:

printf: missing hexadecimal number in escape

Notes: this is causing a failure in the GNU test file tests/printf/printf.sh.