- Change distinct -> typedef.

- Order of attribute declaration is changed for `alias`.
- Added `LANGUAGE_DEV_VERSION` env constant.
- Rename `anyfault` -> `fault`.
- Changed `fault` -> `faultdef`.
- Added `attrdef` instead of `alias` for attribute aliases.

test/test_suite/statements/for_with_optional.c3t

@@ -100,7 +100,7 @@ after_check3:                                     ; preds = %loop.cond
   br label %noerr_block
 panic_block:                                      ; preds = %assign_optional
   %4 = insertvalue %any undef, ptr %error_var, 0
-  %5 = insertvalue %any %4, i64 ptrtoint (ptr @"$ct.anyfault" to i64), 1
+  %5 = insertvalue %any %4, i64 ptrtoint (ptr @"$ct.fault" to i64), 1
   store %any %5, ptr %varargslots, align 16
   %6 = insertvalue %"any[]" undef, ptr %varargslots, 0
   %"$$temp" = insertvalue %"any[]" %6, i64 1, 1

test/test_suite/statements/foreach_custom_errors.c3

@@ -4,7 +4,7 @@ fn void test1()
     foreach (a : x) { }; // #error: It's not possible to enumerate an expression of type 'int'
 }
 
-distinct Test1 = int;
+typedef Test1 = int;
 
 fn void test2()
 {

test/test_suite/statements/foreach_distinct_iterable.c3t

@@ -1,7 +1,7 @@
 // #target: macos-x64
 module test;
 import std;
-distinct TypeA = char[];
+typedef TypeA = char[];
 
 fn char TypeA.get(self, usz i) @operator([]) {
 	return ((char[])self)[i];

test/test_suite/statements/foreach_distinct_pointer_1506.c3

@@ -1,4 +1,4 @@
-distinct Type = char*;
+typedef Type = char*;
 fn usz Type.len(str)
 {
 	return 0;

test/test_suite/statements/foreach_r_custom_errors.c3

@@ -4,7 +4,7 @@ fn void test1()
     foreach_r (a : x) { }; // #error: It's not possible to enumerate an expression of type 'int'
 }
 
-distinct Test1 = int;
+typedef Test1 = int;
 
 fn void test2()
 {

test/test_suite/statements/if_only_throw.c3t

@@ -2,7 +2,7 @@
 module foo;
 import std::io;
 
-fault ABC;
+faultdef ABC;
 
 fn void? test()
 {

test/test_suite/statements/switch_errors.c3

@@ -135,7 +135,7 @@ fn void test_missing_no_cases(Baz x)
     }
 }
 
-fault DIVISION_BY_ZERO;
+faultdef DIVISION_BY_ZERO;
 
 // Rethrowing an error uses "!!" suffix
 fn void? testMayError()

test/test_suite/statements/various_switching.c3t

@@ -3,8 +3,8 @@ module mymodule;
 
 extern fn void printf(char *, ...);
 
-fault FOO;
-fault BAR, BAZ;
+faultdef FOO;
+faultdef BAR, BAZ;
 
 fn void test()
 {