Makefile: Fix malformed manpages

The generated manpage contains malformed .HP directives:
    .HP \w'\fBstop\fR\ 'u \fBstop\fR [\fIpid_file\fR]

The .HP directive takes one argument, the indentation. Thus, the first
line (which is not indented) should be on the next line:
    .HP \w'\fBstop\fR\ 'u
    \fBstop\fR [\fIpid_file\fR]

Manpages will be converted to mdoc(7) in master so we are sure of
the formatting. The DocBook versions will be dropped. This will also
simplify the build process.

References #1180.
[#143563295]

Author: dumbbell

Makefile

@@ -201,6 +201,8 @@ clean-extra-sources:
 	    opt='--stringparam man.indent.verbatims=0' ; \
 	xsltproc --novalid $(DOCS_DIR)/examples-to-end.xsl $< > $<.tmp && \
 	xmlto -vv -o $(DOCS_DIR) $$opt man $< 2>&1 | (grep -v '^Note: Writing' || :) && \
+	awk -F"'u " '/^\.HP / { print $$1; print $$2; next; } { print; }' "$@" > "$@.tmp" && \
+	mv "$@.tmp" "$@" && \
 	test -f $@ && \
 	rm $<.tmp