pgpool: Fix memory leak in a SSL module.

Fix memory leak in a SSL module.

load_dh_file() leaked memory when supplied DH parameters are not
valid. It should have freed the memory returned by
PEM_read_DHparams() using DH_free(). The module was first imported
from PostgreSQL (commit 573bd08b99e277026e87bb55ae69c489fab321b8
2018/1/19) on 2019/6/18 by commit
51bc494aaa7fd191e14038204d18effe2efb0ec8. PostgreSQL found the memory
leak later on and fixed it by commit
e835e89a0fd267871e7fbddc39ad00ee3d0cb55c on 2021/3/20. So we need to
fix it as well.

While I'm at it, the copyright notice in the same file is fixed. Since
the code was copied from PostgreSQL, we should retain the original
PostgreSQL copyright notice.

Author: Tatsuo Ishii <ishii(at)postgresql(dot)org>
Discussion: https://www.postgresql.org/message-id/20260403.091842.102589579921239540.ishii%40postgresql.org
Backpatch-through: v4.3

Branch
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V4_4_STABLE

Details
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https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=205d1c43978b77a5ca9c2155b5090014d0ef35a3

Modified Files
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src/utils/pool_ssl.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)