newlib: Make effects of 'cygnus' explicit

Add all the effects of 'cygnus' for which there exists an explicit way
to request that behaviour:

* Implied foreign strictness and options no-installinfo, no-dependencies
and no-dist are added to AM_INIT_AUTOMAKE in newlib/acinclude.m4.

* macro AM_MAINTAINER_MODE is added to newlib/acinclude.m4.

* For the implied TEXINFO_TEX of '$(top_srcdir)/../texinfo/texinfo.tex',
an explicit TEXINFO_TEX is always relative to $(srcdir), so write the
same pathname in that form.

This is to prepare for the removal of the automake option '--cygnus'.

newlib/acinclude.m4

@@ -120,7 +120,8 @@ AC_SUBST(newlib_basedir)
 
 AC_CANONICAL_HOST
 
-AM_INIT_AUTOMAKE([cygnus no-define 1.9.5])
+AM_INIT_AUTOMAKE([cygnus foreign no-installinfo no-dependencies no-dist no-define 1.9.5])
+AM_MAINTAINER_MODE()
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES(yes)])
 
 # FIXME: We temporarily define our own version of AC_PROG_CC.  This is

newlib/libc/Makefile.am

@@ -224,6 +224,7 @@ targetdep.tex: stmp-targetdep ; @true
 
 $(SUBDEFS): stmp-targetdep ; @true
 
+TEXINFO_TEX = ../../texinfo/texinfo.tex
 info_TEXINFOS = libc.texinfo
 libc_TEXINFOS = sigset.texi extra.texi posix.texi stdio64.texi iconvset.texi \
 	targetdep.tex $(SUBDEFS)

newlib/libm/Makefile.am

@@ -35,8 +35,8 @@ endif
 
 $(SUBLIBS):
 
+TEXINFO_TEX = ../../texinfo/texinfo.tex
 info_TEXINFOS = libm.texinfo
-
 libm_TEXINFOS = targetdep.tex
 
 libm.dvi: targetdep.tex math/stmp-def complex/stmp-def fenv/stmp-def