pgsql: Refactor logic to check for ASCII-only characters in string

Refactor logic to check for ASCII-only characters in string

The same logic was present for collation commands, SASLprep and
pgcrypto, so this removes some code.

Author: Michael Paquier
Reviewed-by: Stephen Frost, Heikki Linnakangas
Discussion: https://postgr.es/m/X9womIn6rne6Gud2@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/93e8ff8701a65a70ea8826bdde7fdbbd9c285477

Modified Files
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contrib/pgcrypto/pgp-pgsql.c         | 18 +++---------------
src/backend/commands/collationcmds.c | 24 ++++--------------------
src/common/saslprep.c                | 19 ++-----------------
src/common/string.c                  | 16 ++++++++++++++++
src/include/common/string.h          |  1 +
5 files changed, 26 insertions(+), 52 deletions(-)