Binary search improvements

Modified the algorithm so that the index is either the location of the
element if found or the index at which to insert the element to maintain
sorted order.

Also added some tests to verify the above claim.

tests/core/slice/test_core_slice.odin

@@ -30,6 +30,7 @@ when ODIN_TEST {
 main :: proc() {
 	t := testing.T{}
 	test_sort_with_indices(&t)
+	test_binary_search(&t)
 
 	fmt.printf("%v/%v tests successful.\n", TEST_count - TEST_fail, TEST_count)
 	if TEST_fail > 0 {
@@ -180,3 +181,59 @@ test_sort_by_indices :: proc(t: ^testing.T) {
 		}
 	}
 }
+
+@test
+test_binary_search :: proc(t: ^testing.T) {
+	index: int
+    found: bool
+
+    test_search :: proc(s: []i32, v: i32) -> (int, bool) {
+		fmt.printf("Searching for %v in %v\n", v, s)
+		index, found := slice.binary_search(s, v)
+		fmt.printf("index: %v\nfound: %v\n", index, found)
+
+		return index, found
+    }
+
+    s := []i32{0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55}
+
+	index, found = test_search(s, 13)
+	assert(index == 9, "Expected index to be 9.")
+	assert(found == true, "Expected found to be true.")
+
+	index, found = test_search(s, 4)
+	assert(index == 7, "Expected index to be 7.")
+	assert(found == false, "Expected found to be false.")
+
+	index, found = test_search(s, 100)
+	assert(index == 13, "Expected index to be 13.")
+	assert(found == false, "Expected found to be false.")
+
+	index, found = test_search(s, 1)
+	assert(index >= 1 && index <= 4, "Expected index to be 1, 2, 3, or 4.")
+	assert(found == true, "Expected found to be true.")
+
+	index, found = test_search(s, -1)
+	assert(index == 0, "Expected index to be 0.")
+	assert(found == false, "Expected found to be false.")
+
+	a := []i32{}
+
+	index, found = test_search(a, 13)
+	assert(index == 0, "Expected index to be 0.")
+	assert(found == false, "Expected found to be false.")
+
+	b := []i32{1}
+
+	index, found = test_search(b, 13)
+	assert(index == 1, "Expected index to be 1.")
+	assert(found == false, "Expected found to be false.")
+
+	index, found = test_search(b, 1)
+	assert(index == 0, "Expected index to be 0.")
+	assert(found == true, "Expected found to be true.")
+
+	index, found = test_search(b, 0)
+	assert(index == 0, "Expected index to be 0.")
+	assert(found == false, "Expected found to be false.")
+}