100% effectively on Windows

The mysqltest docs state that the 'replace_result' command
doesn't perform any escape processing.
However the current implementation was processing backslash 
escapes in the from/to strings.
This prevents replacing e.g. patch on windows (where backslash
is used as a path separator).
Fixed by removing the backslash escape processing from 
'replace_result'.


client/mysqltest.c:
  Bug #36041: remove the escape processing from --replace_result
mysql-test/r/mysqltest.result:
  Bug #36041: test case
mysql-test/t/mysqltest.test:
  Bug #36041: test case