Avoid use of c++ reserved keyword "virtual" when using a C++ compiler.

Avoids requiring nasty hacks around libdrm headers in the new C++
parts of Mesa drivers.

include/drm/drm.h

@@ -373,7 +373,11 @@ struct drm_buf_pub {
  */
 struct drm_buf_map {
 	int count;		/**< Length of the buffer list */
+#ifdef __cplusplus
+	void *virt;
+#else
 	void *virtual;		/**< Mmap'd area in user-virtual */
+#endif
 	struct drm_buf_pub *list;	/**< Buffer information */
 };
 

intel/intel_bufmgr.h

@@ -66,7 +66,11 @@ struct _drm_intel_bo {
 	 * Virtual address for accessing the buffer data.  Only valid while
 	 * mapped.
 	 */
+#ifdef __cplusplus
+	void *virt;
+#else
 	void *virtual;
+#endif
 
 	/** Buffer manager context associated with this buffer object */
 	drm_intel_bufmgr *bufmgr;
@@ -168,7 +172,7 @@ void drm_intel_bufmgr_fake_set_fence_callback(drm_intel_bufmgr *bufmgr,
 drm_intel_bo *drm_intel_bo_fake_alloc_static(drm_intel_bufmgr *bufmgr,
 					     const char *name,
 					     unsigned long offset,
-					     unsigned long size, void *virtual);
+					     unsigned long size, void *virt);
 void drm_intel_bo_fake_disable_backing_store(drm_intel_bo *bo,
 					     void (*invalidate_cb) (drm_intel_bo
 								    * bo,