Check for "plain" option
Add "include config.mk" line to generated Makefiles
Output "DEPDIR=.deps" in Makefile.in

This is needed because it is used in Makefile include directives, and we
don't want the error messages about *.Po files masking those about a missing
config.mk.
Stop "config.mk" being default target using .DEFAULT_GOAL
Track AM_SUBST_NOTMAKE as configure script is run
Minor formatting
Substitute am__nodep as a make macro instead
Allow config.status to find "include *.Po" lines in Makefiles
Use $(V) instead of @AM_V@ for plain Makefiles
Remove old, unused code
Allow the use of different *.am fragments in plain mode
Set am__AMDEP_{TRUE,FALSE} autoconf output variables

These are set according to whether dependency checking is enabled at
configure time. They evaluate to '' or '@: ' and enable or disable commands
in the Makefile.
Use new conditional system for AMDEP throughout depend2.amp
Start on making configure-time conditionals work with verbosity flags

Quite major changes in m4/depend.m4
Fix bugs in dependency rules for non-generic and --disable-dependency-tracking
Combine unverbose printing statements
Add new plain mode fragment "header-vars.amp"
Use plain include directives for *.Po dependency files
Remove autoconf substitution variables from header-vars.amp
Code to find header-vars.amp