makeqstrdata: Work with older Python

This construct (which I added without sufficient testing,
apparently) is only supported in Python 3.7 and newer.  Make it
optional so that this script works on other Python versions.  This
means that if you have a system with non-UTF-8 encoding you will
need to use Python 3.7.

In particular, this affects a problem building circuitpython in
github's ubuntu-18.04 virtual environment when Python 3.7 is not
explicitly installed.  cookie-cuttered libraries call for Python
3.6:
```
    - name: Set up Python 3.6
      uses: actions/setup-python@v1
      with:
        python-version: 3.6
```
Since CircuitPython's own build calls for 3.8, this problem was not
detected.

This problem was also encountered by discord user mdroberts1243.

The failure I encountered was here:
https://github.com/jepler/Jepler_CircuitPython_udecimal/runs/1138045020?check_suite_focus=true
.. while my step of "clone and build circuitpython unix port" is
unusual, I think the same problem would have affected "build assets"
if that step had been reached.

py/makeqstrdata.py

@@ -17,8 +17,9 @@ import collections
 import gettext
 import os.path
 
-sys.stdout.reconfigure(encoding='utf-8')
+if hasattr(sys.stdout, 'reconfigure'):
-sys.stderr.reconfigure(errors='backslashreplace')
+    sys.stdout.reconfigure(encoding='utf-8')
+    sys.stderr.reconfigure(errors='backslashreplace')
 
 py = os.path.dirname(sys.argv[0])
 top = os.path.dirname(py)