pgsql: Change InputFunctionCall* to take a const char *str

Change InputFunctionCall* to take a const char *str

It's reasonable to specify that the input string passed to these
functions isn't modified.

In each case, the input string is passed down to CStringGetDatum(),
which already takes a const char *, so this change just pushes that
API specification one level up.

A couple of callers benefit from this by no longer having to cast away
a const qualifier.

A few more functions that call input functions internally are changed
so that they can now offer a const qualified input string to their
callers.

Reviewed-by: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Discussion: https://www.postgresql.org/message-id/flat/459217ca-3840-4452-8cd1-8f9b47e8d479%40eisentraut.org

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/5767fece95ccb58c25cee0567dd83457b8e15b37

Modified Files
--------------
contrib/postgres_fdw/postgres_fdw.c | 4 ++--
src/backend/bootstrap/bootstrap.c | 6 +++---
src/backend/parser/parse_type.c | 2 +-
src/backend/statistics/extended_stats_funcs.c | 2 +-
src/backend/utils/adt/domains.c | 2 +-
src/backend/utils/adt/rowtypes.c | 2 +-
src/backend/utils/fmgr/fmgr.c | 8 ++++----
src/include/bootstrap/bootstrap.h | 2 +-
src/include/fmgr.h | 8 ++++----
src/include/parser/parse_type.h | 2 +-
10 files changed, 19 insertions(+), 19 deletions(-)