REORG: use the name "sample" instead of "pattern" to designate extracted data

This is mainly a massive renaming in the code to get it in line with the
calling convention. Next patch will rename a few files to complete this
operation.
diff --git a/include/proto/stick_table.h b/include/proto/stick_table.h
index 7756623..f7d650a 100644
--- a/include/proto/stick_table.h
+++ b/include/proto/stick_table.h
@@ -48,8 +48,8 @@
 struct stksess *stktable_update_key(struct stktable *table, struct stktable_key *key);
 struct stktable_key *stktable_fetch_key(struct stktable *t, struct proxy *px,
 				        struct session *l4, void *l7, unsigned int opt,
-				        struct pattern_expr *expr);
-int stktable_compatible_pattern(struct pattern_expr *expr, unsigned long table_type);
+				        struct sample_expr *expr);
+int stktable_compatible_sample(struct sample_expr *expr, unsigned long table_type);
 int stktable_get_data_type(char *name);
 struct proxy *find_stktable(const char *name);