fix(material/select): Allow typography mixin to consume 2018 style configs

See angular#21059 for context.

Author: mmalerba

src/material/select/_select-theme.scss

@@ -2,6 +2,7 @@
 @import '../core/theming/theming';
 @import '../core/style/private';
 @import '../core/style/form-common';
+@import '../core/typography/typography';
 @import '../core/typography/typography-utils';
 
 
@@ -64,6 +65,7 @@
 }
 
 @mixin mat-select-typography($config-or-theme) {
+  $config: mat-private-typography-normalized-config(mat-get-typography-config($config-or-theme));
   $config: mat-get-typography-config($config-or-theme);
   // The unit-less line-height from the font config.
   $line-height: mat-line-height($config, input);