tests: Make it easier to grep failures out of the log file.
launch: Print attach-method, tmpdir, umask, euid when launching.

These are only printed when debugging is enabled, but should help
debugging hard-to-pin-down permissions problems.
ruby: Support 'make INSTALLDIRS=vendor install' for Ruby as well as Perl.

As with Perl, you can now set INSTALLDIRS to control where Ruby places
its files (ie. in the site dir, which is the default, or in the vendor
dir).

The difference in file layout between 'make install' and
'make INSTALLDIRS=vendor install' is shown below (for Fedora 18).

--- /tmp/site	2013-03-14 12:14:35.740015694 +0000
+++ /tmp/vendor	2013-03-14 12:14:13.668093944 +0000
@@ -119,21 +119,20 @@
 ./usr/lib64/ocaml/guestfs/mlguestfs.cmxa
 ./usr/lib64/ocaml/stublibs/dllmlguestfs.so
 ./usr/lib64/ocaml/stublibs/dllmlguestfs.so.owner
-./usr/lib64/perl5/auto/Sys/Guestfs/Guestfs.bs
-./usr/lib64/perl5/auto/Sys/Guestfs/Guestfs.so
-./usr/lib64/perl5/auto/Sys/Guestfs/.packlist
 ./usr/lib64/perl5/perllocal.pod
-./usr/lib64/perl5/Sys/bindtests.pl
-./usr/lib64/perl5/Sys/Guestfs/Lib.pm
-./usr/lib64/perl5/Sys/Guestfs.pm
+./usr/lib64/perl5/vendor_perl/auto/Sys/Guestfs/Guestfs.bs
+./usr/lib64/perl5/vendor_perl/auto/Sys/Guestfs/Guestfs.so
+./usr/lib64/perl5/vendor_perl/auto/Sys/Guestfs/.packlist
+./usr/lib64/perl5/vendor_perl/Sys/bindtests.pl
+./usr/lib64/perl5/vendor_perl/Sys/Guestfs/Lib.pm
+./usr/lib64/perl5/vendor_perl/Sys/Guestfs.pm
 ./usr/lib64/php/modules/guestfs_php.so
 ./usr/lib64/pkgconfig/libguestfs-gobject-1.0.pc
 ./usr/lib64/pkgconfig/libguestfs.pc
 ./usr/lib64/python2.7/site-packages/guestfs.py
 ./usr/lib64/python2.7/site-packages/libguestfsmod.la
 ./usr/lib64/python2.7/site-packages/libguestfsmod.so
-./usr/local/lib64/ruby/site_ruby/_guestfs.so
-./usr/local/share/ruby/site_ruby/guestfs.rb
+./usr/lib64/ruby/vendor_ruby/_guestfs.so
 ./usr/sbin/libguestfs-make-fixed-appliance
 ./usr/share/doc/libguestfs/example-debian-netinst-cd.xml
 ./usr/share/doc/libguestfs/example-debian.xml
@@ -406,3 +405,4 @@
 ./usr/share/man/uk/man3/guestfs-perl.3
 ./usr/share/man/uk/man3/guestfs-python.3
 ./usr/share/man/uk/man3/guestfs-ruby.3
+./usr/share/ruby/vendor_ruby/guestfs.rb

For prompting me to fix this, thanks: Hilko Bengen.
README: Discourage general users from doing 'make install'.

It causes plenty of problems with people have multiple parallel
versions of libguestfs installed, and there's no benefit because you
can easily run libguestfs and tools from the build directory.