build does not need xml1sec-openssl

[oss-aimoto]

I built v0.18.0 on CentOS8(xmlsec1-openssl-devel package is not installed).
I get an error in ./configure.

configure: error: Package requirements (xmlsec1-openssl) were not met:

checking xml1sec-openssl in this commit, but I think it's xml1sec correctly.
xmlenc.h is under the xml1sec directory.

/usr/include/xmlsec1/xmlsec/xmlenc.h

[thijskh]

At least on Debian it does not matter much because liblasso transitively depends on it in any case.

[simo5]

technically you can use xmlsec1 with other crypto libraries, if a patch were contributed to change this it would be accepted.