pgsql: Break out OpenSSL-specific code to separate files.

Break out OpenSSL-specific code to separate files.

This refactoring is in preparation for adding support for other SSL
implementations, with no user-visible effects. There are now two #defines,
USE_OPENSSL which is defined when building with OpenSSL, and USE_SSL which
is defined when building with any SSL implementation. Currently, OpenSSL is
the only implementation so the two #defines go together, but USE_SSL is
supposed to be used for implementation-independent code.

The libpq SSL code is changed to use a custom BIO, which does all the raw
I/O, like we've been doing in the backend for a long time. That makes it
possible to use MSG_NOSIGNAL to block SIGPIPE when using SSL, which avoids
a couple of syscall for each send(). Probably doesn't make much performance
difference in practice - the SSL encryption is expensive enough to mask the
effect - but it was a natural result of this refactoring.

Based on a patch by Martijn van Oosterhout from 2006. Briefly reviewed by
Alvaro Herrera, Andreas Karlsson, Jeff Janes.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/680513ab79c7e12e402a2aad7921b95a25a4bcc8

Modified Files
--------------
configure                                |    2 +-
configure.in                             |    2 +-
src/backend/libpq/Makefile               |    4 +
src/backend/libpq/auth.c                 |   14 +-
src/backend/libpq/be-secure-openssl.c    | 1045 +++++++++++++++++++++
src/backend/libpq/be-secure.c            | 1027 +--------------------
src/backend/libpq/hba.c                  |    2 +-
src/backend/postmaster/fork_process.c    |    4 +-
src/backend/utils/init/postinit.c        |    8 +-
src/backend/utils/misc/guc.c             |    3 -
src/bin/psql/command.c                   |    4 +-
src/include/libpq/libpq-be.h             |   24 +-
src/include/libpq/libpq.h                |    9 +
src/include/pg_config.h.in               |    6 +-
src/include/pg_config.h.win32            |    6 +-
src/include/pg_config_manual.h           |    9 +
src/interfaces/libpq/Makefile            |    4 +
src/interfaces/libpq/fe-connect.c        |    7 +-
src/interfaces/libpq/fe-misc.c           |    4 +-
src/interfaces/libpq/fe-secure-openssl.c | 1468 +++++++++++++++++++++++++++++
src/interfaces/libpq/fe-secure.c         | 1469 ++----------------------------
src/interfaces/libpq/libpq-int.h         |   37 +-
src/interfaces/libpq/win32.mak           |   12 +-
src/tools/msvc/Mkvcbuild.pm              |   12 +
src/tools/msvc/Solution.pm               |    4 +-
src/tools/msvc/config_default.pl         |    2 +-
26 files changed, 2771 insertions(+), 2417 deletions(-)