Some AIX specific changes to Xmd.h for X11R7.1.

First the char datatype on AIX is unsigned by default and the check for AIX is
obsolete.
***************
*** 139,145 ****
  typedef short INT16;
  #endif
  
! #if defined(__STDC__) || defined(sgi) || defined(AIXV3)
  typedef signed char    INT8;
  #else
  typedef char           INT8;
--- 139,145 ----
  typedef short INT16;
  #endif
  
! #if defined(__STDC__) || defined(sgi) || defined(_AIX)
  typedef signed char    INT8;
  #else
  typedef char           INT8;

I really want to get away from using _AIX, but __STDC__ is not defined for
all our compilers.  Other suggestions here are certainly welcome.

Next, even when compiled in 32-bit mode some of our ddx code needs the
CARD64 data type defined.

***************
*** 150,155 ****
--- 150,158 ----
  typedef unsigned int CARD32;
  #else
  typedef unsigned long CARD32;
+ #endif
+ #if !defined(WORD64) && !defined(LONG64)
+ typedef unsigned long long CARD64;
  #endif
  typedef unsigned short CARD16;
  typedef unsigned char  CARD8;