* Makefile.tpl: Rearrange by moving recursive_targets rules
into their proper sections.
* Makefile.tpl (top level bootstrap support): Move disabling
of coverage flags from 'make' to 'configure'; improve comments.
* Makefile.in: Regenerate.
* Makefile.tpl (experimental top level bootstrap) Move stage1
language setting from all- target to configure- target; disable
intermodule optimization in stage 1; prevent gratuitous rebuilds
of stage 1.
* Makefile.in: Regenerate.
* configure.in: Comma-separate stage 1 language list for top
level bootstrap.
* configure: Regenerate.
* Makefile.tpl: Clean up experimental top level bootstrap support:
note known problems; set CONFIG_SHELL; don't set BUILD_CC; relocate
prev-gcc in configure- targets as well as all- targets.
* Makefile.in: Regenerate.