[patch] fake out vtable.h during Configure.pl

[Josh Wilmes]

I'm fiddling with a compiler called tcc (i'll add it to tinderbox 
shortly).  It was complaining that struct _vtable was not completely 
defined while building one of the test programs in Configure.pl.  It was 
right- at that point we generate an empty version of vtable.h, so this 
struct isn't defined.

I've stuck in a dummy definition which allows it to get past that point:

Index: Configure.pl
===================================================================
RCS file: /home/perlcvs/parrot/Configure.pl,v
retrieving revision 1.71
diff -u -r1.71 Configure.pl
--- Configure.pl        4 Jan 2002 22:13:58 -0000       1.71
+++ Configure.pl        5 Jan 2002 05:58:01 -0000
@@ -499,6 +499,7 @@
     my %newc;
 
     open NEEDED, ">include/parrot/vtable.h";
+    print NEEDED "/* dummy */ struct _vtable { int a; };\n";
     close NEEDED;
     buildfile("testparrotsizes_c");
     compiletestc("testparrotsizes");