Fix the Requires() examples by adding a sleep command to the

Fix the Requires() examples by adding a sleep command to the
infrastructure and using it to force the SConstruct file(s) to generate
version.c files with new timestamps each run.  Fix the description of
the example, since the verson.o file does get recompiled each run, but
the use of Requires() means the downstream hello executable doesn't get
relinked because of it.

git-svn-id: http://scons.tigris.org/svn/scons/trunk@4624 fdb21ef1-2011-0410-befe-b5e4ea1792b1