Allow building with gcc-4.4

With this small patch, building succeeds with Debian's current gcc-snapshot,
gcc (Debian 20081130-1) 4.4.0 20081130 (experimental) [trunk revision 142292]

That gcc also warns about the remaining #idents in
  vvp/concat.cc
  vvp/dff.h

The resulting build shows some regressions in the test suite, that
I am still investigating.  The patch does not break building, or show
test suite regressions, with gcc-4.3.

syn-rules.y

@@ -356,7 +356,7 @@ static int yylex()
 {
       if (ptr_ == 0) {
 	    yylval = 0;
-	    return EOF;
+	    return 0;
       }
 
       yylval = ptr_;

tgt-vhdl/vhdl_syntax.hh

@@ -21,6 +21,7 @@
 #ifndef INC_VHDL_SYNTAX_HH
 #define INC_VHDL_SYNTAX_HH
 
+#include <inttypes.h>
 #include "vhdl_element.hh"
 #include "vhdl_type.hh"