Added the []= overloadable operator and implemented it for vector, map, and string

tests/test_bracket_assign.expected_results

@@ -0,0 +1 @@
+bracket assign: index: 4, rhs: 9

tests/test_bracket_assign.krak

@@ -0,0 +1,16 @@
+import io:*
+
+obj BracketAssign {
+    fun operator[]=(index:int, rhs:int) {
+        print("bracket assign: index: ")
+        print(index)
+        print(", rhs: ")
+        println(rhs)
+    }
+}
+
+fun main():int {
+    var test:BracketAssign
+    test[4] = 9
+    return 0
+}

tests/test_map.expected_results

@@ -4,4 +4,5 @@
 3
 20
 2
+30
 4

tests/test_map.krak

@@ -10,9 +10,11 @@ fun main():int {
     println(m[3])
     m.set(3,4)
     m.set(4,20)
+    m[6] = 30
     println(m[1])
     println(m[4])
     println(m[2])
+    println(m[6])
     println(m[3])
     return 0
 }

tests/test_string.expected_results

@@ -6,3 +6,4 @@ hope
 hope3
 new way!
 a
+now win!

tests/test_string.krak

@@ -16,6 +16,10 @@ fun main(): int {
     var newWay = string::string("new way!")
     io::println(newWay)
     io::println(newWay[5])
+    newWay.set(1, 'o')
+    newWay[5] = 'i'
+    newWay[6] = 'n'
+    io::println(newWay)
     return 0;
 }
 

tests/test_vectorTest.expected_results

@@ -25,5 +25,10 @@ find test
 0
 1
 2
+set and []= test
+4
+8
+9
+7
 done
 Destroyed: 0

tests/test_vectorTest.krak

@@ -111,6 +111,13 @@ fun main(): int {
     println(multipleFindTest.find_index(2))
     println(multipleFindTest.find_index(3))
 
+    println("set and []= test")
+    var setTest = vector(4,5,6)
+    setTest.add(7)
+    setTest.set(1,8)
+    setTest[2] = 9
+    setTest.do(fun(it: int) println(it);)
+
     println("done")
 
     return 0;