wget: implement TLS verification with ENABLE_FEATURE_WGET_OPENSSL

wget: implement TLS verification with ENABLE_FEATURE_WGET_OPENSSL

When ENABLE_FEATURE_WGET_OPENSSL is enabled, correctly implement TLS
verification by default. And only ignore verification errors, if
--no-check-certificate was passed.

Also note, that previously OPENSSL implementation did not implement
TLS verification, nor printed any warning messages that verification
was not performed.

Bug-Ubuntu: https://bugs.launchpad.net/bugs/1879533

CVE-2018-1000500

Signed-off-by: Dimitri John Ledkov <xnox@ubuntu.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>