- properly require openssl (status quo, just use a correct parameter)
 - explicitly require system libpcap (status quo)
 - explicitly require system libpcre [1]
 - explicitly require zlib (status quo)
 - explicitly require system libssh2 [2]
 - explicitly require system lua5.3 [3]
 - adjust makedepends accordingly

[1] System pcre is newer and properly configured for mips*.
[2] This is the ./configure default, just make sure the choice is stable.
[3] This is the ./configure default, just let it find the system version.

check() passes on x86_64 and mipseln8hf at least, however this commit does
not re-enable it due to unclear aarch64 / arm* status.