Add a draft manual page describing the input syntax accepted by the
`isa` utility.

Ticket:	#412


git-svn-id: https://elftoolchain.svn.sourceforge.net/svnroot/elftoolchain/trunk@2900 95820547-d848-0410-985e-9ae8fe0fa350
Add the `isa.5` manual page to the build.

Ticket:	#412

git-svn-id: https://elftoolchain.svn.sourceforge.net/svnroot/elftoolchain/trunk@2901 95820547-d848-0410-985e-9ae8fe0fa350
Fix a bug: correctly loop over input files.

Ticket:	#412

git-svn-id: https://elftoolchain.svn.sourceforge.net/svnroot/elftoolchain/trunk@2902 95820547-d848-0410-985e-9ae8fe0fa350
 * Use the current option syntax in the `check-specifications` make target.
 * Add the instruction set specification added in changeset [2899] to
   the list of specifications to be checked by this target.

Ticket:	#412

git-svn-id: https://elftoolchain.svn.sourceforge.net/svnroot/elftoolchain/trunk@2903 95820547-d848-0410-985e-9ae8fe0fa350