execve: fix support of personalities with different word size

* execve.c (printargc): Do not assume that host and target pointers have
the same size.
* tests/execve.c: New file.
* tests/execve.expected: Likewise.
* tests/execve-v.expected: Likewise.
* tests/execve.test: New test.
* tests/Makefile.am (check_PROGRAMS): Add execve.
(TESTS): Add execve.test.
(EXTRA_DIST): Add execve.expected and execve-v.expected.
* tests/.gitignore: Add execve.
7 files changed