ecpg: avoid breaking the IDENT precedence level in two.

Careless string hacking caused parse.pl to transform gram.y's
declaration

%nonassoc    IDENT PARTITION RANGE ROWS ...

into

%nonassoc IDENT
%nonassoc CSTRING PARTITION RANGE ROWS ...

It turns out that this has no semantic impact, because the
generated preproc.c is exactly the same either way (if you
inject a blank line to keep line numbers the same).

Nonetheless, given the great emphasis that the commentary in
gram.y places on keeping those other keywords at the same
precedence level as IDENT, this seems like foolishly risking ecpg
behaving differently from the core parser.  Adjust the code so
that CSTRING is added to the precedence line without breaking it
into two lines.

Discussion: https://postgr.es/m/2157151.1713540065@sss.pgh.pa.us

Author: tglsfdc

src/interfaces/ecpg/preproc/parse.pl

@@ -289,11 +289,10 @@ sub main
 				# Accumulate the line in $str.
 				$str = $str . ' ' . $a;
 
-				# HACK: insert our own %nonassoc line after IDENT.
-				# XXX: this seems pretty wrong, IDENT is not last on its line!
+				# Give our token CSTRING the same precedence as IDENT.
 				if ($a eq 'IDENT' && $arr[0] eq '%nonassoc')
 				{
-					$str = $str . "\n%nonassoc CSTRING";
+					$str = $str . " CSTRING";
 				}
 			}
 			# Save the lightly-processed line in orig_tokens.