Add information about line contents on parsing failure of wait_event_names.txt

The contents of the line whose parsing failed was not reported in the
error message produced by generate-wait_event_types.pl, making harder
than necessary the debugging of incorrectly-shaped entries in the file.

Reported-by: Andres Freund
Discussion: https://postgr.es/m/ZK9S3jFEV1X797Ll@paquier.xyz

src/backend/utils/activity/generate-wait_event_types.pl

@@ -72,7 +72,7 @@ my @lines_sorted =
 # Read the sorted lines and populate the hash table
 foreach my $line (@lines_sorted)
 {
-	die "unable to parse wait_event_names.txt"
+	die "unable to parse wait_event_names.txt for line $line\n"
 	  unless $line =~ /^(\w+)\t+(\w+)\t+(\w+)\t+("\w.*\.")$/;
 
 	(   my $waitclassname,