Deorbit the netscape plugin

Netscape hasn't been a thing since 2008.

We would only try to build it if someone manually ran 'webinstall'
in src/libuafs, and there is no documentation telling anyone to do so.

It's dead, Jim.

Change-Id: I7486ca33da7ff19f23f0d9f54f5fb4e7e3232540
Deorbit separate JUAFS build

Since 80943970b8cfcdf3fc630b25804aebaea228bd73, when the web enhancements
were enabled universally, there has no longer been a functional difference
between the UAFS and JUAFS builds.  Their object files are compiled
using the same compilation rule, and the list of object files differed
only by rx_kmutex.o (which is devoid of content) and xdr_int32.o
(which is preumably an oversight).

Save the extra build time by just reinstalling libuafs.a as libjuafs.a
to preserve the existing interfaces.

Additionally, drop the LIBJUAFS make variable -- all definitions set
it to libjuafs.a.  Similarly, the LIBJUAFS_FLAGS variable was unused
and can be removed.

Change-Id: I2074d5bc26e326db36b16e055431818ef1c69210
Build libuafs with lwptool

Use the standard program for building slightly different object files
into their own directories, instead of rolling our own.  This allows
us to pull the build rules into the Makefile.common, leaving just
compiler flags and similar in the MakefileProtos.

We do have to hack around the standard libtool build rules a little
bit in order to get things compiled using the same compiler and arguments
that the old build system used, but it does not seem too bad.

As a side effect, we get rid of the LIBUAFS make variable -- all sites
were defining it to libuafs.a anyway, so we can just hardcode it.

Change-Id: I2bda2f40bbd0aa808c24e074d2d7bcd329f6b77e