A few small fixes so code compiles with g++.

src/libqhull.h

@@ -751,7 +751,7 @@ struct qhT {
   realT last_newhigh;
   unsigned lastreport;    /* for qh_buildtracing */
   int mergereport;        /* for qh_tracemerging */
-  void *old_qhstat;       /* for saving qh_qhstat in save_qhull() and UsingLibQhull.  Free with qh_free() */
+  qhstatT *old_qhstat;       /* for saving qh_qhstat in save_qhull() and UsingLibQhull.  Free with qh_free() */
   setT *old_tempstack;    /* for saving qhmem.tempstack in save_qhull */
   int   ridgeoutnum;      /* number of ridges for 4OFF output (qh_printbegin,etc) */
 };

src/mem.h

@@ -114,7 +114,7 @@ struct qhmemT {               /* global memory management variables */
   void    *curbuffer;         /* current buffer, linked by offset 0 */
   void    *freemem;           /*   free memory in curbuffer */
   int 	   freesize;          /*   size of freemem in bytes */
-  void 	  *tempstack;         /* stack of temporary memory, managed by users */
+  setT 	  *tempstack;         /* stack of temporary memory, managed by users */
   FILE    *ferr;              /* file for reporting errors, only user is qh_fprintf() */
   int      IStracing;         /* =5 if tracing memory allocations */
   int      cntquick;          /* count of quick allocations */