`libelftc` test suite:
 * Correct an error in a test case message.
 * Add a test case to check the validity of the indices returned when
   the string pool is resized.

Ticket:	#361

git-svn-id: https://elftoolchain.svn.sourceforge.net/svnroot/elftoolchain/trunk@2862 95820547-d848-0410-985e-9ae8fe0fa350