MFC r303188,r303190,r303271,r303438,r303453: Warn flags for gcc 6.1

MFC r303188,r303190,r303271,r303438,r303453: Warn flags for gcc 6.1

  r303188 (by br):
    Add warn flags for GCC 6.1 compiler.
  r303190 (by br):
    Add GCC 6.1 warn flags for kernel as well.
  r303271 (by br):
    Fix style.
  r303438 (by br):
    o Add warn flags required to build modules with GCC 6.1;
    o Sort GCC 4.8 warn flags.
  r303453 (by br):
    Normalise the CWARNFLAGS inter-word spacing: remove all leading and
    trailing space, and convert multiple consecutive spaces to single
    space.

Approved by:	markj (mentor)