Fix #96 by setting the timestamp in the COFF header. VC2005's incremental linker...

Fix #96 by setting the timestamp in the COFF header.  VC2005's incremental linker uses the
timestamp to determine if the object file has been updated, so not setting it makes for
bad behavior (the object file gets updated, but when the executable is linked it uses the
older "internal" version).

To keep tests passing, check an environment variable (YASM_TEST_SUITE); if this exists, the
timestamp is set to 0.  Set this environment variable in out_test.sh.

svn path=/trunk/yasm/; revision=1742