Update smdlexp.vcxproj

Added a relative path to the required Module definition File smdlexp.def
found in halflife\utils\smdlexp

Although the project will compile fine without this step, 3DSMAX will
fail to load the plug-in giving errors such as "smdlexp.dle doesn't
implement LibVersion"

It seems that smdlexp.def needs to be explicitly defined in the vcxproj
in order to work.
Update to smdlexp.vcxproj

Added Module definition File to linker input for all configurations,
previously only added to debug as spotted by @ripieces Also changed the
relative pathing to $(ProjectDir)..\..\utils\smdlexp\smdlexp.def ->
Cleaner and makes more sense :)
Merge pull request #1531 from thefoofighter/master

Update to smdlexp.vcxproj