os.date crashes wlua

[Stuart P. Bentley]

If you call os.date with a non-ANSI-C-valid format string (eg. not "D" but "%D"), Lua Windows Standalone Interpreter will encounter a problem and need to close.

[Stuart P. Bentley (stuart)]

This is an error in Lua caused by an error in Windows (crashing if undefined strings get sent to its functions). Lua 5.2 is slated to "fix" this by having all parameters not defined in ANSI C cause a Lua error.

[Stuart P. Bentley (stuart)]

If this really ruins anybody's day, I've created a branch at lp:~stuart/sandpad/wrapunsafe with a "valid.lua" containing a table of all the valid C-defined parameters strftime as a starting point for writing a wrapper around os.date (and io.open, which also has this problem).