* Makefile.tpl (configure-stage[+id+]-[+prefix+][+module+],
all-stage[+id+]-[+prefix+][+module+], : Use $(current_stage) instead
of `cat stage_current`. Always provide the `r' and `s' variables.
(clean-stage[+id+]-[+prefix+][+module+]): Likewise, and make it into
a single shell execution.
(configure-[+prefix+][+module+], all-[+prefix+][+module+]): For
bootstrapped modules, make the stage1 module if the build was not
started yet, else build the current stage.
(all-host, all-target): Omit bootstrapped modules (if bootstrapping).
(all-build, all-host, all-target, [+make_target+]-host,
[+make_target+]-target): Do not use \-continued lines.
(target modules): Depend on stage_last, not all-gcc, if bootstrapping.
(current_stage, restrap, stage_last): New.