newlines: fix mixed newlines to LF-only

I use the curl repo mainly on Windows with the typical Windows git
checkout which converts the LF line endings in the curl repo to CRLF
automatically on checkout. The automatic conversion is not done on files
in the repo with mixed line endings. I recently noticed some weird
output with projects/build-openssl.bat that I traced back to mixed line
endings, so I scanned the repo and there are files (excluding the
test data) that have mixed line endings.

I used this command below to do the scan. Unfortunately it's not as easy
as git grep, at least not on Windows. This gets the names of all the
files in the repo's HEAD, gets each of those files raw from HEAD, checks
for mixed line endings of both LF and CRLF, and prints the name if
mixed. I excluded path tests/data/test* because those can have mixed
line endings if I understand correctly.

for f in `git ls-tree --name-only --full-tree -r HEAD`;
do if [ -n "${f##tests/data/test*}" ];
    then git show "HEAD:$f" | \
     ...