Use xsltproc/dblatex instead of fop in Build-Depends, enable verbose execution with...

Use xsltproc/dblatex instead of fop in Build-Depends, enable verbose execution with --no-xmllint for a2px

The verbose execution provides us with:

| a2x: executing: "xmllint" --nonet --noout --valid "/tmp/buildd/zsh-lovers-0.8.3/zsh-lovers.1.xml"
|
| I/O error : Attempt to load network entity http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd
| /tmp/buildd/zsh-lovers-0.8.3/zsh-lovers.1.xml:2: warning: failed to load external entity "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"
| D DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"
|                                                                                ^
| /tmp/buildd/zsh-lovers-0.8.3/zsh-lovers.1.xml:5: validity error : Validation failed: no DTD found !
| <refentry lang="en">
|                    ^
|
| make[1]: *** [all] Error 1

instead of:

| a2x: ERROR: "xmllint" --nonet --noout --valid "/tmp/buildd/zsh-lovers-0.8.3/zsh-lovers.1.xml" returned non-zero exit status 4

And we don't seem to be able to build with xmllint inside the
tool chain even though the output looks OK-ish, so let's
run it with --no-xmllint