Delete unused files

[mahrud]

This directory contains several simple utilities that either are not used or can be replaced with simpler tools:

• args.c: not used
• echoout.c: used once in Macaulay2/d to reverse a list. Possible alternative:
  • alias tac='perl -e "print reverse(<>)"' (in case tac doesn't already exist)
  • (for d in ${MY_LIST}; do echo $$d; done) | tac
• gc_demo.c: not used, though perhaps useful to keep it somewhere else for pedagogy.
• gc_test.c: used as a test, can be moved to Macaulay2/tests
• linkexec*: seems to be an overly complicated solution to making the programs relocatable
• setup.c: windows legacy
• timestamp.c: compiled, but not used as far as I can tell