Part of our module implementation adds a sample mapper server, the
guts of which are used by the default in-process mapping of cc1plus.
Rather than add another executable to gcc/cp/, this creates a new
c++tools directory where this and any other c++ tools might live.
The toplevel changes are a subsequent commit, because ... git.
c++tools/ChangeLog:
* Makefile.in: New.
* config.h.in: New.
* configure: New.
* configure.ac: New.
* resolver.cc: New.
* resolver.h: New.
* server.cc: New.
