Create debian/control without preexisting debian/control

Previously, the rule in debian/rules to create debian/control expected
an older debian/control to be present and tried to back it up, which
failed if there was no debian/control. Fix this by only doing the backup
when debian/control exists.
Fixed the name of the cacao and jamvm packages
Remove generated file debian/control
Change "watch" url to let uscan find the jdk8u20-b18 upstream package

I can't update http://87.98.165.193/checkjdk.php, so using the GitHub
wiki connected to this repository seems like a reasonable workaround. In
the mid to long term, we should use Debian's fakeupstream.cgi
(http://qa.debian.org/cgi-bin/fakeupstream.cgi).
Update to upstream version jdk8u20-b18

Patches in debian/patches have been changed/refreshed as follows:

Deleted:

sparc-stubgenerator.diff
	(has been added upstream in a slightly different form)

Adapted to changes in upstream code:

accessible-toolkit.patch
hotspot-powerpcspe.diff
system-lcms.patch

Adjusted to new offset in upstream code:

default-jvm-cfg-default.diff
dnd-files.patch
fix-jtreg-location.patch
hotspot-sparc-arch.diff
ld-symbolic-functions-default.diff
system-libjpeg.patch
system-libpng.patch

Whitespace change in patch formatting:

zero-missing-headers.diff
Use Debian's fakeupstream.cgi service to find upstream archives

Now that https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=751873 is
closed, there's no need for a special watch page any more as long as we
use the newest upstream version. :-)