version stamper -- have vers stamper check file content first

[Fred T. Hamster]

problem::::

noticed that hoople/clam on linux is
always recompiling all EXEs when the version changes.

first of all, that's silly. the version isn't used on linux at all.

second of all, that's silly. when things do get a new version, things
shouldn't need relinking unless the so/dll actually changed somehow.

how can we minimize these recompilations?

solution::::

if the file's already there,
read it in.

if file contents are
identical to what would have been written,
don't say anything about the version.
don't write the file.
get out.

only if one of the version.rc or version.h files
had to be written should we say anything.