Precompute and inline constant globals

This is necessary so that other constant globals referencing constant globals can be precomputed as well (NON_STANDALONE_FLOW in binaryen)

tests/compiler/enum.wast

@@ -0,0 +1,76 @@
+(module
+ (type $i (func (result i32)))
+ (type $v (func))
+ (global $enum/Implicit.ZERO i32 (i32.const 0))
+ (global $enum/Implicit.ONE i32 (i32.const 1))
+ (global $enum/Implicit.TWO i32 (i32.const 2))
+ (global $enum/Implicit.THREE i32 (i32.const 3))
+ (global $enum/Explicit.ZERO i32 (i32.const 0))
+ (global $enum/Explicit.ONE i32 (i32.const 1))
+ (global $enum/Explicit.TWO i32 (i32.const 2))
+ (global $enum/Explicit.THREE i32 (i32.const 3))
+ (global $enum/Mixed.ZERO i32 (i32.const 0))
+ (global $enum/Mixed.ONE i32 (i32.const 1))
+ (global $enum/Mixed.THREE i32 (i32.const 3))
+ (global $enum/Mixed.FOUR i32 (i32.const 4))
+ (global $enum/NonConstant.ZERO (mut i32) (i32.const 0))
+ (global $enum/NonConstant.ONE (mut i32) (i32.const 0))
+ (memory $0 1)
+ (data (i32.const 4) "\08\00\00\00")
+ (export "memory" (memory $0))
+ (start $start)
+ (func $enum/getZero (; 0 ;) (type $i) (result i32)
+  (return
+   (i32.const 0)
+  )
+ )
+ (func $start (; 1 ;) (type $v)
+  (set_global $enum/NonConstant.ZERO
+   (call $enum/getZero)
+  )
+  (set_global $enum/NonConstant.ONE
+   (i32.add
+    (get_global $enum/NonConstant.ZERO)
+    (i32.const 1)
+   )
+  )
+ )
+)
+(;
+[program.elements]
+  clz
+  ctz
+  popcnt
+  rotl
+  rotr
+  abs
+  ceil
+  copysign
+  floor
+  max
+  min
+  nearest
+  sqrt
+  trunc
+  current_memory
+  grow_memory
+  unreachable
+  load
+  store
+  reinterpret
+  select
+  sizeof
+  isNaN
+  isFinite
+  assert
+  enum/Implicit
+  enum/Explicit
+  enum/Mixed
+  enum/getZero
+  enum/NonConstant
+[program.exports]
+  enum/Implicit
+  enum/Explicit
+  enum/Mixed
+  enum/NonConstant
+;)