dynamic_library: use RTLD_LAZY by default
dynamic_library: use RTLD_LAZY by default

You can still override it manually, but this seems to be the recommended
default mode. From OS X's `man dlopen`:

"RTLD_LAZY is normally preferred, for reasons of efficiency.  However,
RTLD_NOW is useful to ensure that any undefined symbols are discovered during
the call to dlopen()."

This should at least prevent the "undefined symbol" errors in #80.

lzpfmh/node-ffi,unbornchikken/node-ffi,node-ffi/node-ffi,skoky/node-ffi,pmuellr/node-ffi,craigcomstocks/node-ffi,paulcbetts/node-ffi,skoky/node-ffi,Icenium/node-ffi,craigcomstocks/node-ffi,unrealsolver/node-ffi,skoky/node-ffi,paulcbetts/node-ffi,unrealsolver/node-ffi,Icenium/node-ffi,node-ffi/node-ffi,pmuellr/node-ffi,paulcbetts/node-ffi,Icenium/node-ffi,unrealsolver/node-ffi,unbornchikken/node-ffi,unrealsolver/node-ffi,node-ffi/node-ffi,lzpfmh/node-ffi,skoky/node-ffi,lzpfmh/node-ffi,pmuellr/node-ffi,Icenium/node-ffi,pmuellr/node-ffi,unbornchikken/node-ffi,paulcbetts/node-ffi,node-ffi/node-ffi,craigcomstocks/node-ffi,lzpfmh/node-ffi,craigcomstocks/node-ffi,unbornchikken/node-ffi