x11glvndserver: Use MODULEVERSIONSTRING instead of hard-coding "NVIDIA Corporation"

The X headers define MODULEVENDORSTRING like so:

  #ifndef MODULEVENDORSTRING
  #define MODULEVENDORSTRING      "X.Org Foundation"
  #endif

This allows module vendors such as NVIDIA to override the vendor string at build
time, rather than hard-coding "NVIDIA Corporation" in the sources.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Kyle Brenneman <kbrenneman@nvidia.com>
Fixes #48.

src/x11glvnd/x11glvndserver.c

@@ -135,7 +135,7 @@ static ExtensionModule glvExtensionModule = {
 static XF86ModuleVersionInfo x11glvndVersionInfo =
 {
     "x11glvnd",
-    "NVIDIA Corporation",
+    MODULEVENDORSTRING,
     MODINFOSTRING1,
     MODINFOSTRING2,
     XORG_VERSION_NUMERIC(4,0,2,0,0),