A tentative fix of #16380. It adds "line" everywhere...

This also reduces binary size slightly (cmd/go on ARM as an example):

			before		after
total binary size	8068097		8018945 (-0.6%)
.gopclntab		1195341		1179929 (-1.3%)
.debug_line		 689692		 652017 (-5.5%)

Change-Id: Ibda657c6999783c5bac180cbbba487006dbf0ed7
Reviewed-on: https://go-review.googlesource.com/25082Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>