Docs build failure

[Neil Puttock]

Hi everybody,

I've just tried to do a clean build, and there are two problems
related to some recent patches:

1. ouput-count doesn't work, which causes the regression test
clip-systems.ly to fail:

 82       \markup { \epsfile #X #30.0 #(format #f
"~a-1-from-2.0.1-to-4.0.1-clip.eps" (ly:parser-output-name parser)) }

This file can't be found, since the there's no `1' inserted due to
ouput-count being ignored.

2. using ly:format in make-ps-images causes scaling of PNGs to fail
for multi-page snippets:

Converting to `./wtk1-fugue2.pdf'...
touch ./out-www/baerenreiter-sarabande.png

Converting to 
PNG.../home/neil/lilypond/out/share/lilypond/current/scm/ps-to-png.scm:73:7:
In procedure rename-file in expression (rename-file file old):
/home/neil/lilypond/out/share/lilypond/current/scm/ps-to-png.scm:73:7:
No such file or directory
make[4]: *** [out-www/wtk1-fugue2.pdf] Error 1

Here's the line which formats the filename for each PNG:

113           (pngn (format  "~a-page%d.~a" base extension))

The rename fails when scaling since the percent sign is now escaped;
for the Bach example, the two original PNGs are named as follows:

wtk1-fugue2-page\1.png
wtk1-fugue2-page\2.png

Regards,
Neil