Autoheader plan

I want to make pg_config.h.in be automatically generated by autoheader
so we don't have to edit it by hand, but there is a lot of stuff in
pg_config.h.in that isn't directly generated by configure, so it needs
to be moved elsewhere.

Here's what I want to do:

Move DEF_NBUFFERS and DEF_MAXBACKENDS to the header files where
NBuffers and MaxBackends are declared. Remove --with-maxbackends
configure option. There's no need for users to edit these at compile
time.

All of the remaining code from "part 2" of the existing pg_config.h.in
will be moved to a separate file (maybe pg_config_manual.h?) and will
be unaffected by autoheader and configure.

Everything in part 1 and 3 can be automatically generated.

Move inclusion of pg_config_os.h to c.h. That means c.h will contain
the following code near the top:

#include pg_config.h
#include pg_config_manual.h
#include pg_config_os.h

(Perhaps the first one should be renamed to pg_config_auto.h for
parallelism?)

All code in part 5 will be moved to c.h section 8, which contains
similar code already anyway.

--
Peter Eisentraut peter_e(at)gmx(dot)net