Fix two warnings reported by Ubuntu clang version 3.2-1~exp9ubuntu1 (tags/RELEASE_32/final) (based on LLVM 3.2)

gant.c:194:8: warning: variable 'r' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
   if (fd > 0)
       ^~~~~~
gant.c:199:11: note: uninitialized use occurs here
   return r;
          ^
gant.c:194:4: note: remove the 'if' if its condition is always true
   if (fd > 0)
   ^~~~~~~~~~~
gant.c:191:10: note: initialize the variable 'r' to silence this warning
   uint r;
         ^
          = 0
gant.c:268:31: warning: format specifies type 'unsigned int' but the argument has type 'unsigned long' [-Wformat]
      fprintf(out, "0x%04x:", offset + i);
                      ~~~~    ^~~~~~~~~~
                      %04lx