Merge branch '16-t-varop-mm' into 21-debug
Merge branch '25-from-2.15.1' into 27-more-news
R_BIT_BUCKET just a simple define in vars.mk, since conditional define is only gmake
Merge branch '21-debug' into 27-more-news
Merge branch '21-debug' into 28
update doc on R_BIT_BUCKET
Merge branch '27-more-news' into 28