It is annoying when imenu generates index also for functions found in
comments area.  e.g., in c-mode:

/*
a : Modified filesys_init()
  : hello
*/

uint8 filesys_init( void )
    {
    }

imenu will generate two filesys_init, which makes imenu useless.

This patch skips comment area completely.  In this case, it will
generate only one filesys_init.