[client] implemented renderer specific option API

Please note the vsync and mipmap options are now specific to OpenGL
To configure them use the following options:

  -o opengl:mipmap=1
  -o opengl:vsync=0

client/lg-renderer.c

@@ -0,0 +1,50 @@
+/*
+Looking Glass - KVM FrameRelay (KVMFR) Client
+Copyright (C) 2017 Geoffrey McRae <geoff@hostfission.com>
+https://looking-glass.hostfission.com
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 2 of the License, or (at your option) any later
+version.
+
+This program is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+Place, Suite 330, Boston, MA 02111-1307 USA
+*/
+
+#include "lg-renderer.h"
+
+#include <string.h>
+
+bool LG_RendererValidatorBool(const char * value)
+{
+  if (!value)
+    return false;
+
+  return
+    (strcasecmp(value, "1"      ) == 0) ||
+    (strcasecmp(value, "0"      ) == 0) ||
+    (strcasecmp(value, "true"   ) == 0) ||
+    (strcasecmp(value, "false"  ) == 0) ||
+    (strcasecmp(value, "yes"    ) == 0) ||
+    (strcasecmp(value, "no"     ) == 0) ||
+    (strcasecmp(value, "on"     ) == 0) ||
+    (strcasecmp(value, "off"    ) == 0) ||
+    (strcasecmp(value, "enable" ) == 0) ||
+    (strcasecmp(value, "disable") == 0);
+}
+
+bool LG_RendererValueToBool(const char * value)
+{
+  return
+    (strcasecmp(value, "1"      ) == 0) ||
+    (strcasecmp(value, "true"   ) == 0) ||
+    (strcasecmp(value, "yes"    ) == 0) ||
+    (strcasecmp(value, "on"     ) == 0) ||
+    (strcasecmp(value, "enable" ) == 0);
+}