Proposed macros for error fields

I propose to add the following macros for the fields of an error or notice
message for use in libpq applications.  The names are modelled after the
ones that ODBC uses.  (Well, at least they are chosen not to collide in
case we want to continue on that track.)

S    PG_DIAG_SEVERITY
C    PG_DIAG_SQLSTATE
M    PG_DIAG_MESSAGE_PRIMARY
D    PG_DIAG_MESSAGE_DETAIL
H    PG_DIAG_MESSAGE_HINT
P    PG_DIAG_STATEMENT_POSITION
W    PG_DIAG_STACK_TRACE
F    PG_DIAG_SOURCE_FILE
L    PG_DIAG_SOURCE_LINE
R    PG_DIAG_SOURCE_FUNCTION

Comments?

-- 
Peter Eisentraut   peter_e@gmx.net