UTF-8 is the proper naming according to the UTF-8 RFC and is also the
name used for a similar keyword in the file() command. This commit
brings (backward compatible) consistency to the keyword names and allows
the standard UTF-8 name to be used with execute_process(). The old UTF8
keyword is still supported.
Use the KWSys Process "MergeOutput" option to give the child process
the same pipe (or file) for both stdout and stderr. This allows
natural merging of stdout and stderr together instead of merging
on arbitrary buffered read boundaries as before.
