make: VERSION variable can be set either via git or the VERSION file

Change up the shell line so that it can fallback on the VERSION file
if building without a Git repository (eg, from a release tarball).

Additionally, change the titlepic generation so that it uses this
single instance of setting VERSION rather than doing its own thing.

Makefile

@@ -27,7 +27,7 @@
 # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-VERSION=$(shell git describe)
+VERSION=$(shell git describe 2>/dev/null || cat VERSION)
 WADS=wads
 CPP=scripts/simplecpp
 DEUTEX=deutex
@@ -44,7 +44,7 @@ all: $(OBJS)
 
 subdirs:
 	$(MAKE) -C graphics/text
-	$(MAKE) -C graphics/titlepic
+	$(MAKE) VERSION=$(VERSION) -C graphics/titlepic
 	$(MAKE) -C lumps/cph/misc-lumps
 	$(MAKE) -C lumps/genmidi
 	$(MAKE) -C lumps/dmxgus

graphics/titlepic/create_caption

@@ -1,7 +1,5 @@
 #!/bin/sh
 
-VERSION=`git describe` || VERSION=`cat ../../VERSION`
-
 convert titlepic.gif -fill white -font Helvetica-Bold                  \
   -draw "image over 94,2 0,0 '$1'"                                     \
   -pointsize 20                                                        \