MFC: Sync with -CURRENT installation document cleanup.

alpha/Makefile 1.3->1.4
alpha/artifcle.sgml 1.1->1.2
common/abstract.sgml 1.1
common/floppies.sgml (deleted)
common/install.ent 1.1->1.2
common/install.sgml 1.6->1.7
common/layout.sgml 1.3->1.4
common/trouble.sgml 1.2->1.3
common/upgrade.sgml 1.2->1.3
i386/Makefile 1.3->1.4
i386/article.sgml 1.1->1.2

Approved by: murray (implicitly)