Applies a command to all translations of a translation catalog.
The COMMAND can be any program that reads a translation from standard
input. It is invoked once for each translation. Its output becomes
msgexecs output. msgexecs return code is the maximum return code
across all invocations.
A special builtin command called 0 outputs the translation, followed by a
null byte. The output of "msgexec 0" is suitable as input for "xargs -0".
Mandatory arguments to long options are mandatory for short options too.