Added Unicode compliance test for trim() function.

Author: springcomp

tests/compliance/string_functions.json

@@ -61,6 +61,11 @@
       { "expression": "trim(' subject string ', 'su ')", "result": "bject string" },
       { "expression": "trim(' subject string ', 'gsu ')", "result": "bject strin" },
 
+      {
+        "expression": "trim('\u0009\u000A\u000B\u000C\u000D\u0020\u0085\u00A0\u1680\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u2028\u2029\u202F\u205F\u3000')",
+        "result": ""
+      },
+
       { "expression": "trim_left(' subject string ')", "result": "subject string " },
       { "expression": "trim_left(' subject string ', 's')", "result": " subject string " },
       { "expression": "trim_left(' subject string ', 'su')", "result": " subject string " },