Some more gitignore cleanups: cover contrib and PL regression test outputs.

Also do some further work in the back branches, where quite a bit wasn't
covered by Magnus' original back-patch.

src/pl/plperl/.gitignore

@@ -2,3 +2,6 @@
 /Util.c
 /perlchunks.h
 /plperl_opmask.h
+
+# Generated subdirectories
+/results/

src/pl/plpgsql/src/.gitignore

@@ -1,2 +1,4 @@
 /pl_gram.c
 /pl_gram.h
+/pl.tab.h
+/pl_scan.c

src/pl/plpython/.gitignore

@@ -0,0 +1,2 @@
+# Generated subdirectories
+/results/

src/pl/tcl/.gitignore

@@ -0,0 +1,2 @@
+# Generated subdirectories
+/results/

src/pl/tcl/modules/.gitignore

@@ -0,0 +1,3 @@
+/pltcl_delmod
+/pltcl_listmod
+/pltcl_loadmod