[patch] a_Dpip_send_cmd

http://www.inventati.org/noname/dillo/dpip-send-cmd.patch

Patch adds a_Dpip_send_cmd and helper function a_Dpip_vbuild_cmd.

This way common pattern

  d_cmd = a_Dpip_build_cmd(format, ...);
  st = a_Dpip_dsh_write_str(sh, flush, d_cmd);
  dFree(d_cmd);

can be replaced with

  st = a_Dpip_send_cmd(sh, flush, format, ...);