set to 'en' there -- Windows does not understand the 'en_US' locale.
The test succeeds there.

fixes bug #414940, and redoes the fix for #129417 in a different way.
It also fixes a number of other problems with locale-specific formatting:
If there is leading or trailing spaces, then no grouping should be applied
in the spaces, and the total length of the string should not be changed
due to grouping.
Also added test case which works only if the en_US locale is available.