- Ignore intermediate progress updates.

- Support locales that use a character other than period as decimal
  separator (eg 100,0%).

test1148 checks that the progress finishes at 100% and has the right
bar width. Prior to this change the test assumed that the only progress
reported for such a quick transfer was 100%, however in rare instances
(like in the CI where transfer time can slow considerably) there may be
intermediate updates. For example, below is stderrlog1148 from a failed
CI run with explicit \r and \n added (it is one line; broken up so that
it's easier to understand).

\r
\r##################################                                        48.3%
\r######################################################################## 100.0%
\n

Closes https://github.com/curl/curl/pull/5194

"precheck command error" is not very helpful.

Modifying the locale with environment variables doesn't work for native
Windows applications. Just disable the test in this case if the decimal
separator is something different than a point. Use a precheck with a
small C program to achieve that.

Closes https://github.com/curl/curl/pull/2786

Set mode="text" when line endings depend on the system representation.

Closes https://github.com/curl/curl/pull/2772

Fixes #2446
Closes #2488

...as otherwise it might use a different decimal sign.

Bug: #2436
Reported-by: Oumph on github

Closes #1569