This is a back port from development of the code to put and check
that the vvp input file is the right version. It also adds the -V
flag to vvp. It does not add the VERSION_TAG information so will
only produce the single string ivl_version tag. The runtime will
read both forms since if it is feed a V0.9 file we want it to
complain nicely (no syntax error). To change the displayed version
for the various programs and checks change version.h.
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