fix bug in filters parser

Parser parsed "a or (b or c) and d" into "a or b or c and d". ("and" has higher operator precedence)

It was caused by a premature flattening of the expressions (a or (b or c) => a or b or c) while still parsing the expression. This did not regard that an operator with higher precedence than at the current point in parsing may follow next.

library/src/commonMain/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/BooleanExpressionBuilder.kt

@@ -50,8 +50,6 @@ internal class BooleanExpressionBuilder<I : Matcher<T>, T> {
         {
             node = node.parent!!
         }
-
-        node.flatten()
     }
 
     fun addValue(i: I) {

library/src/commonTest/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/TagFilterExpressionParserTest.kt

@@ -458,7 +458,16 @@ internal class TagFilterExpressionParserTest {
         notMatches(mapOfKeys("a", "b", "c", "d"), expr)
     }
 
-
+    @Test fun brackets_are_not_dissolved_illegally() {
+        val expr = "a or (b or c) and !d"
+        matches(mapOfKeys("a"), expr)
+        matches(mapOfKeys("a", "d"), expr)
+        matches(mapOfKeys("b"), expr)
+        matches(mapOfKeys("c"), expr)
+        notMatches(mapOfKeys("c", "d"), expr)
+        notMatches(mapOfKeys("b", "d"), expr)
+        matches(mapOfKeys("a", "c", "d"), expr)
+    }
 
     @Test fun fail_on_placeholder_not_closed() {
         shouldFail("{my placeholder")