Modes for which Font Lock mode is automagically turned on.
Global Font Lock mode is controlled by the command `global-font-lock-mode'.
If nil, means no modes have Font Lock mode automatically turned on.
If t, all modes that support Font Lock mode have it automatically turned on.
If a list, it should be a list of `major-mode' symbol names for which Font Lock
mode should be automatically turned on. The sense of the list is negated if it
begins with `not'. For example:
means that Font Lock mode is turned on for buffers in C and C++ modes only.