Fix loading of the SMBFS kernel module. The KMODDEPS line in the SMBFS

Fix loading of the SMBFS kernel module.  The KMODDEPS line in the SMBFS
Makefile generated incorrect (read fake) symbols; the build system was
pretty satisified but kldload was not and returned ENOEXEC.

Instead, add a Makefile for libiconv as it is supposed to be, because
SMBFS requires it as a module dependency.

Note, the SMBFS module needs to be recompiled for it to work, and the
libiconv KLD needs to be built using the newly added Makefile.  Also
rebuild 'libmchain'.