cmd/internal/gc: more Node cleanups

More cleanups to gc.Node

- make Node.Local a boolean
- make Type.Local a boolean
- reduce the size of Node.Esc to a uint8

Reducing the size of Node.Esc shaves ~45mb off the RSS compiling cmd/internal/gc on amd64

before:
        Maximum resident set size (kbytes): 659496
after:
        Maximum resident set size (kbytes): 612196

- declare gc.Funcdepth as int32
- declare Node.Funcdepth as int32

In both cases, these were previously machine specific int types. This doesn't result in
any memory saving at the moment due to struct padding.

Change-Id: Iabef8da15e962fe8b79d7fd3d402fb26ce7ec31c
Reviewed-on: https://go-review.googlesource.com/7261
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/internal/gc/syntax.go

@@ -40,26 +40,26 @@ type Node struct {
 	Nowritebarrier bool  // emit compiler error instead of write barrier
 	Walkdef        uint8
 	Typecheck      uint8
-	Local          uint8
+	Local          bool
 	Dodata         uint8
 	Initorder      uint8
 	Used           bool
 	Isddd          bool // is the argument variadic
 	Readonly       bool
 	Implicit       bool
-	Addrtaken      bool // address taken, even if not moved to heap
-	Assigned       bool // is the variable ever assigned to
-	Captured       bool // is the variable captured by a closure
-	Byval          bool // is the variable captured by value or by reference
-	Dupok          bool // duplicate definitions ok (for func)
-	Wrapper        bool // is method wrapper (for func)
-	Reslice        bool // this is a reslice x = x[0:y] or x = append(x, ...)
-	Likely         int8 // likeliness of if statement
-	Hasbreak       bool // has break statement
-	Needzero       bool // if it contains pointers, needs to be zeroed on function entry
-	Needctxt       bool // function uses context register (has closure variables)
-	Esc            uint // EscXXX
-	Funcdepth      int
+	Addrtaken      bool  // address taken, even if not moved to heap
+	Assigned       bool  // is the variable ever assigned to
+	Captured       bool  // is the variable captured by a closure
+	Byval          bool  // is the variable captured by value or by reference
+	Dupok          bool  // duplicate definitions ok (for func)
+	Wrapper        bool  // is method wrapper (for func)
+	Reslice        bool  // this is a reslice x = x[0:y] or x = append(x, ...)
+	Likely         int8  // likeliness of if statement
+	Hasbreak       bool  // has break statement
+	Needzero       bool  // if it contains pointers, needs to be zeroed on function entry
+	Needctxt       bool  // function uses context register (has closure variables)
+	Esc            uint8 // EscXXX
+	Funcdepth      int32
 
 	// most nodes
 	Type *Type