Rename def to alias.

test/test_suite/struct/const_zero_init_1360.c3t

@@ -2,7 +2,7 @@
 module test;
 import std::collections::map;
 
-def Foo = HashMap{String, HashMap{String, String}};
+alias Foo = HashMap{String, HashMap{String, String}};
 macro test()
 {
     HashMap{String, String} map0;

test/test_suite/struct/member_expr.c3

@@ -1,7 +1,7 @@
 
-def Func = fn int(int);
+alias Func = fn int(int);
 
-def Func2 = fn int(Foo*, int);
+alias Func2 = fn int(Foo*, int);
 
 struct Foo
 {

test/test_suite/struct/struct_bad_member.c3

@@ -2,7 +2,7 @@ struct Foo {
   void bar; // #error: Members cannot be of
 }
 
-def Void = void;
+alias Void = void;
 struct Foo2 {
   Void bar; // #error: Members cannot be of
 }

test/test_suite/struct/zero_member.c3

@@ -1,4 +1,4 @@
-def Foo = int[0]; // #error: An array may not have zero
+alias Foo = int[0]; // #error: An array may not have zero
 
 struct Bar
 {