bug(md-select): change the arrow position to absolute (#3580)

Fixes #3112

Author: jefersonestevo

src/lib/select/select.scss

@@ -111,14 +111,22 @@ $mat-select-trigger-font-size: 16px !default;
 }
 
 .mat-select-arrow {
+  position: absolute;
+  right: 0;
   width: 0;
   height: 0;
   border-left: $mat-select-arrow-size solid transparent;
   border-right: $mat-select-arrow-size solid transparent;
   border-top: $mat-select-arrow-size solid;
   margin: 0 $mat-select-arrow-margin;
+
+  [dir='rtl'] & {
+    right: auto;
+    left: 0;
+  }
 }
 
+
 .mat-select-panel {
   @include mat-menu-base();
   padding-top: 0;