Update to latest Snowball sources.

It's been some time since we did this, partly because the upstream
snowball project hasn't formally tagged a new release since 2021.
The main motivation for doing it now is to absorb a bug fix
(their commit e322673a841d9abd69994ae8cd20e191090b6ef4), which
prevents a null pointer dereference crash if SN_create_env() gets
a malloc failure at just the wrong point.  We'll patch the back
branches with only that change, but we might as well do the full
sync dance on HEAD.

Aside from a bunch of mostly-minor tweaks to existing stemmers, this
update adds a new stemmer for Estonian.  It also removes the existing
stemmer for Romanian using ISO-8859-2 encoding.  Upstream apparently
concluded that ISO-8859-2 doesn't provide an adequate representation
of some Romanian characters, and the UTF-8 implementation should be
used instead.

While at it, update the README's instructions for doing a sync,
which have not been adjusted during the addition of meson tooling.

Thanks to Maksim Korotkov for discovering the null-pointer
bug and submitting the fix to upstream snowball.

Reported-by: Maksim Korotkov <m.korotkov@postgrespro.ru>
Discussion: https://postgr.es/m/1d1a46-67ab1000-21-80c451@83151435

1 files changed, 3 insertions, 3 deletions

diff --git a/src/backend/snowball/libstemmer/utilities.c b/src/backend/snowball/libstemmer/utilities.c
index 1ecd2410fe7..8acc18541d5 100644
--- a/src/backend/snowball/libstemmer/utilities.c
+++ b/src/backend/snowball/libstemmer/utilities.c
@@ -281,7 +281,7 @@ extern int find_among(struct SN_env * z, const struct among * v, int v_size) {
         w = v + i;
         if (common_i >= w->s_size) {
             z->c = c + w->s_size;
-            if (w->function == 0) return w->result;
+            if (w->function == NULL) return w->result;
             {
                 int res = w->function(z);
                 z->c = c + w->s_size;
@@ -336,7 +336,7 @@ extern int find_among_b(struct SN_env * z, const struct among * v, int v_size) {
         w = v + i;
         if (common_i >= w->s_size) {
             z->c = c - w->s_size;
-            if (w->function == 0) return w->result;
+            if (w->function == NULL) return w->result;
             {
                 int res = w->function(z);
                 z->c = c - w->s_size;
@@ -429,7 +429,7 @@ extern int slice_from_v(struct SN_env * z, const symbol * p) {
 }
 
 extern int slice_del(struct SN_env * z) {
-    return slice_from_s(z, 0, 0);
+    return slice_from_s(z, 0, NULL);
 }
 
 extern int insert_s(struct SN_env * z, int bra, int ket, int s_size, const symbol * s) {