doc: Prefer an installed version of yat2m

* configure.ac (YAT2M): Check for tool.
* doc/Makefile.am (yat2m-stamp): Use installed tool if possible.
--

configure.ac

@@ -605,6 +605,8 @@ AC_PROG_RANLIB
 AC_CHECK_TOOL(AR, ar, :)
 AC_PATH_PROG(PERL,"perl")
 AC_CHECK_TOOL(WINDRES, windres, :)
+AC_PATH_PROG(YAT2M, "yat2m", "./yat2m" )
+AC_ARG_VAR(YAT2M, [tool to convert texi to man pages])
 AC_ISC_POSIX
 AC_SYS_LARGEFILE
 GNUPG_CHECK_USTAR

doc/Makefile.am

@@ -146,12 +146,12 @@ yat2m-stamp: $(myman_sources) defs.inc
 	@touch yat2m-stamp.tmp
 	incd="`test -f defsincdate || echo '$(srcdir)/'`defsincdate"; \
 	for file in $(myman_sources) ; do \
-              ./yat2m $(YAT2M_OPTIONS) --store \
+              $(YAT2M) $(YAT2M_OPTIONS) --store \
                   --date "`cat $$incd 2>/dev/null`" \
 	          `test -f '$$file' || echo '$(srcdir)/'`$$file ; done
 	@mv -f yat2m-stamp.tmp $@
 
-yat2m-stamp: yat2m
+yat2m-stamp: $(YAT2M)
 
 $(myman_pages) gnupg.7 : yat2m-stamp defs.inc
 	@if test -f $@; then :; else \