Add string.h to the list of default includes for C functions.
Fix bug with Python programs that had syntax errors being shown as correct answers.
Gave up on syntax-colouring editors. EditArea unusable in Chrome and long-term maintainability looking poor. Ace and CodeMirror don't seem to work in a YUI context. So reverted to simple autoindent on ENTER and even simpler replacing of TAB with 4 spaces. Seems to work OK in current Chrome, Firefox and IE. Good enough for simple editing, which is all one ought to be doing in this context anyway.