Move MAIL_USE_FLOCK, MAIL_USE_LOCKF, BLESSMAIL_TARGET from cpp to configure.

Move MAIL_USE_FLOCK, MAIL_USE_LOCKF, BLESSMAIL_TARGET from cpp to configure.

* configure.in (MAIL_USE_FLOCK, MAIL_USE_LOCKF): New AC_DEFINEs.
(BLESSMAIL_TARGET): New output variable.

* lib-src/Makefile.in (BLESSMAIL_TARGET): Set with configure, not cpp.

* src/s/aix4-2.h (MAIL_USE_LOCKF):
* src/s/bsd-common.h (MAIL_USE_FLOCK):
* src/s/darwin.h (MAIL_USE_FLOCK):
* src/s/gnu-linux.h (MAIL_USE_FLOCK):
* src/s/irix6-5.h (MAIL_USE_FLOCK):
* src/s/template.h (MAIL_USE_FLOCK):
Move to configure.

* src/s/ms-w32.h: Comment.

* msdos/sed3v2.inp (BLESSMAIL_TARGET): Edit to need-blessmail.