Merge pull request #32 from retupmoca/master

Fix library extension guessing for MoarVM
fix for: warning: too many arguments for format [-Wformat-extra-args]
fixed typo: libraires -> libraries
Merge pull request #34 from FROGGS/patch-2

fixed typo: libraires -> libraries
Merge pull request #33 from FROGGS/patch-1

fix for: warning: too many arguments for format [-Wformat-extra-args]
use perllibs, because libs contains boilerplate

On my ubunto box nativecall.libs contains -lgdbm which is not needed, and is not found by the linker for some reason.
$ perl -MConfig -E 'say $Config{libs}'
-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
$ perl -MConfig -E 'say $Config{perllibs}'
-ldl -lm -lpthread -lc -lcrypt
Merge pull request #35 from FROGGS/patch-3

use perllibs, because libs contains boilerplate
Allow runtime specification of native library

Previously, the native library was fixed at compiletime. This patch
allows you to modify the native library used at runtime by calling
&sub.libname = 'libfoo' (only effective before first use).