Remove CRAY/WORD64 support (unifdef -UCRAY -UWORD64)

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Replace TXT16 with XChar2b inline

No longer need #define to substitute it now that we no longer set
it to a different type on CRAY systems.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Remove support for pre-C89 headers (unifdef -UX_NOT_STDC_ENV)

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>