Add automake option `subdir-objects'. #28588

git-svn-id: https://svn.sourceforge.jp/svnroot/molds/branches/automake@1694 1136aad2-a195-0410-b898-f5ea1d11b9d8
Downloaded ax_boost_base.m4. #28588

from http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_boost_base.m4

git-svn-id: https://svn.sourceforge.jp/svnroot/molds/branches/automake@1695 1136aad2-a195-0410-b898-f5ea1d11b9d8