Additional error checking

Added some error-checking to login(), and a small function that does a naive
check for attempted SQL injection.

Signed-off-by: Sebastian Lenartowicz <slenarto@uoguelph.ca>
Fixed error in comment in users.php

Fixed an error in a comment that somehow snuck into users.php. Whoops.

Signed-off-by: Sebastian Lenartowicz <slenarto@uoguelph.ca>
Merge branch 'master' of https://github.com/BlackBox3750/System