configure.in: fix FIRSTMAKEFILE config

* configure.in (FIRSTMAKEFILE): AC_CONFIG_FILES needs the file
  arguments separating by a colon literally.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43324 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* remove trailing spaces.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43325 b2dd03c8-39d4-4d8f-98ff-823fe69b080e