waf: add operating system to deps set
waf: os_mac -> os_darwin
waf: fix dict styling
waf: add a custom check for libsmbclient

libsmbclient depends on the linker values detected for libdl and to have those
we need to have the configure context available wehn calling check_libs
waf: keep the libstore lowercase

we just need the defines to be all uppercase (which is already done elsewhere)