pgsql: Fix pg_isblank()

Fix pg_isblank()

There was a pg_isblank() function that claimed to be a replacement for
the standard isblank() function, which was thought to be "not very
portable yet". We can now assume that it's portable (it's in C99).

But pg_isblank() actually diverged from the standard isblank() by also
accepting '\r', while the standard one only accepts space and tab.
This was added to support parsing pg_hba.conf under Windows. But the
hba parsing code now works completely differently and already handles
line endings before we get to pg_isblank(). The other user of
pg_isblank() is for ident protocol message parsing, which also handles
'\r' separately. So this behavior is now obsolete and confusing.

To improve clarity, I separated those concerns. The ident parsing now
gets its own function that hardcodes the whitespace characters
mentioned by the relevant RFC. pg_isblank() is now static in hba.c
and is a wrapper around the standard isblank(), with some extra logic
to ensure robust treatment of non-ASCII characters.

Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://www.postgresql.org/message-id/flat/170308e6-a7a3-4484-87b2-f960bb564afa%40eisentraut.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/8b3e2c622a85208b94808c54d9b40b10b030d304

Modified Files
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src/backend/libpq/auth.c | 17 +++++++++++++----
src/backend/libpq/hba.c | 9 +++------
src/include/libpq/hba.h | 1 -
3 files changed, 16 insertions(+), 11 deletions(-)