build shared versions of libraries

build shared versions of libraries

building defaults to off until clang is updated.

current clang does not handle -shared, necessary to change the ld
invocation to build shared libraries properly. a new clang should be
installed and MKPIC defaults to no unless the newer clang is detected.

changes:

	. mainly small imports of a Makefile or two and small fixes
	  (turning things back on that were turned off in Makefiles)
	. e.g.: dynamic librefuse now depends on dynamic
	  libpuffs, so libpuffs has to be built dynamically too
	  and a make dependency barrier is needed in lib/Makefile
	. all library objects now have a PIC (for .so) and non-PIC
	  version, so everything is built twice.
	. generate PIC versions of the compat (un-RENAMEd) jump files,
	  include function type annotation in generated assembly
	. build progs with -static by default for now
	. also build ld.elf_so
	. also import NetBSD ldd