Change a few Makefile vars using ${} to use $() to match the rest.
Change a few Makefile vars using ${} to use $() to match the rest.

Also get rid of one annoying bright pink (in emacs) orphaned tab.

Signed-off-by: Rob Browning <1dc5917c2adeeba13d1ef33dbb40691a1b67cc65@defaultvalue.org>

apenwarr/bup,gevaerts/bup,mhoeher/bup,ToxicFrog/bup,jbaber/bup,gevaerts/bup,pombredanne/bup,jbaber/bup,tjanez/bup,pombredanne/bup,ToxicFrog/bup,gevaerts/bup,pombredanne/bup,jbaber/bup,ToxicFrog/bup,jbaber/bup,tjanez/bup,mhoeher/bup,gevaerts/bup,ToxicFrog/bup,jbaber/bup,pombredanne/bup,jbaber/bup,mhoeher/bup,pombredanne/bup,mhoeher/bup,apenwarr/bup,tjanez/bup,tjanez/bup,mhoeher/bup,tjanez/bup,ToxicFrog/bup,apenwarr/bup,pombredanne/bup,apenwarr/bup,gevaerts/bup,tjanez/bup,mhoeher/bup