Handle "#" operator properly inside macro. Fix coding bug.

Handle "#" operator properly inside macro.  Fix coding bug.

cc-mode.el (c-neutralize-syntax-in-and-mark-CPP): On finding a "#" which
looks like the start of a macro, check it isn't already inside a macro.

cc-engine.el (c-state-safe-place): Don't record a new "safe" position
into the list of them when this is beyond our current position.