Fixed option -X for strip and elfcopy: Remove compiler generated local
symbols when -X is specified.

git-svn-id: https://elftoolchain.svn.sourceforge.net/svnroot/elftoolchain/trunk@2970 95820547-d848-0410-985e-9ae8fe0fa350
Give a warning when symbol table does not exist while function
generate_symbols() is called.

git-svn-id: https://elftoolchain.svn.sourceforge.net/svnroot/elftoolchain/trunk@2971 95820547-d848-0410-985e-9ae8fe0fa350