pgsql: Fix unportable disregard of alignment requirements in RADIUS cod

Fix unportable disregard of alignment requirements in RADIUS code.

The compiler is entitled to store a char[] local variable with no
particular alignment requirement. Our RADIUS code cavalierly took such
a local variable and cast its address to a struct type that does have
alignment requirements. On an alignment-picky machine this would lead
to bus errors. To fix, declare the local variable honestly, and then
cast its address to char * for use in the I/O calls.

Given the lack of field complaints, there must be very few if any
people affected; but nonetheless this is a clear portability issue,
so back-patch to all supported branches.

Noted while looking at a Coverity complaint in the same code.

Branch
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REL9_6_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/c804c00d38f6a848f0d7e57a05ea5468fc5762b2

Modified Files
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src/backend/libpq/auth.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)