The threee tags `<name>`, `</name>` and `<command>` were frequently used
with a leading space that this removes. The reason this habbit is so
widespread in testcases is probably that they have been copy and pasted.
Hence, fixing them all now might curb this practice from now on.
Closes#12028
mk-lib1521.pl generates a test program (lib1521.c) that calls
curl_easy_setopt() for every known option with a few typical values to
make sure they work (ignoring the return codes).
Some small changes were necessary to avoid asserts and NULL accesses
when doing this.
The perl script needs to be manually rerun when we add new options.
Closes#1543
