Previously we needed to include headers required by the various
sudo*h files. Now those files are more self-sufficient and we
should only include headers needed by code in the various .c files.
1) don't assume snprintf() returns -1 on error, check for <0
2) when comparing return value of sizeof(foo), cast the sizeof, not the len
3) cast return value to void in cases where snprintf cannot fail
run "make tsdump" in the plugins/sudoers directory (it is not built
by default). In order to map the tty device number to a name,
sudo_ttyname_dev() has been moved into libsudo_util.
