A survey among jikes users on the desired behavior of @files on the compiler
command line suggested that each line should be considered a separate token.
That's the only way to support filenames that contain spaces.

javac should adopt this suggestion, but there is a backward compatibility
issue when a line contains something like

-source 1.4

To avoid most problems, tokenize the line when it begins with a dash.
Otherwise consider the contents of the line to be a single token.