Make asciidoc a requirement for building Tinyproxy

asciidoc is necessary as the version number is added during
configure into the asciidoc manpage sources. So simply bundling
a pre-generated manpage won't do.

configure.ac

@@ -279,6 +279,9 @@ AC_SUBST(ADDITIONAL_OBJECTS)
 # Check for asciidoc
 AC_PATH_PROG(A2X, a2x, no)
 AM_CONDITIONAL(HAVE_A2X, test "x$A2X" != "xno")
+if test x"$A2X" = x"no"; then
+  AC_MSG_ERROR([Test for asciidoc failed. See the file 'INSTALL' for help.])
+fi
 
 AC_CONFIG_FILES([
 Makefile

docs/man5/Makefile.am

@@ -15,9 +15,6 @@ else
 	@echo "*** a2x (asciidoc) is required to regenerate $(@) ***"; exit 1;
 endif
 
-EXTRA_DIST = \
-        $(man_MANS)
-
 CLEANFILES = \
 	$(MAN5_FILES:.txt=.5) \
 	$(MAN5_FILES:.txt=.xml)

docs/man8/Makefile.am

@@ -15,9 +15,6 @@ else
 	@echo "*** a2x (asciidoc) is required to regenerate $(@) ***"; exit 1;
 endif
 
-EXTRA_DIST = \
-        $(man_MANS)
-
 CLEANFILES = \
 	$(MAN8_FILES:.txt=.8) \
 	$(MAN8_FILES:.txt=.xml)