rpmspec: add make_install, make_build keywords

%make_install added in RPM 4.8[0]
%make_build added in RPM 4.12[1]

[0]http://rpm.org/gitweb?p=rpm.git;a=commitdiff;h=883253ea6af71f8063d7a045841c35bad22147e2
[1]http://rpm.org/gitweb?p=rpm.git;a=commitdiff;h=89df36524bace71decee4ab4f979d4ffb449c9a7

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>