Integer and memory overflow issues.

Integer and memory overflow issues.

* emacsclient.c (xmalloc): Accept size_t, not unsigned int, to
avoid potential buffer overflow issues on typical 64-bit hosts.
Return void *, not long *.
(get_current_dir_name): Report a failure, instead of looping
forever, if buffer size calculation overflows.  Treat malloc
failures like realloc failures, as that has better behavior and is
more consistent.  Do not check whether xmalloc returns NULL, as
that's not possible.
(message): Do not arbitrarily truncate message to 2048 bytes when
sending it to stderr; use vfprintf instead.
(get_server_config, set_local_socket)
(start_daemon_and_retry_set_socket): Do not alloca
arbitrarily-large buffers; that's not safe.
(get_server_config, set_local_socket): Do not use sprintf when its
result might not fit in 'int'.
(set_local_socket): Do not assume uid fits in 'int'.