* fhandler.h (fhandler_dev_mem): Add method `init'. Add members

`mem_size' and `init_phase'.
        * fhandler_mem.cc (init): New function to figure out the size of
        the physical memory.
        (open): Add checking for illegal flags. Change usage of access mode.
        (write): Add intended functionality.
        (read): Add parameter checking. Eliminate page size constant. Use
        getpagesize() instead. Don't touch errno and don't create debug output
        while init() is running.
        (lseek): Add bounds checking. Fix SEEK_END.
        (fstat): Eliminate page size constant. Use getpagesize() instead.
        (dup): Add intended functionality.

winsup/cygwin/fhandler.h

@@ -767,7 +767,11 @@ public:
 class fhandler_dev_mem: public fhandler_base
 {
 protected:
+  unsigned long mem_size;
   unsigned long pos;
+  bool init_phase;
+
+  void init (void);
 
 public:
   fhandler_dev_mem (const char *name, int unit);