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>
diff --git a/src/cmd/internal/gc/reflect.go b/src/cmd/internal/gc/reflect.go
index 36aa0b6..19694ad 100644
--- a/src/cmd/internal/gc/reflect.go
+++ b/src/cmd/internal/gc/reflect.go
@@ -1000,7 +1000,7 @@
 	}
 
 	// named types from other files are defined only by those files
-	if tbase.Sym != nil && tbase.Local == 0 {
+	if tbase.Sym != nil && !tbase.Local {
 		return s
 	}
 	if isforw[tbase.Etype] {