runtime: rename close to closefd

Avoids shadowing the builtin channel close function.

Change-Id: I7a729b0937c8248fe27222be61318a88db995eee
Reviewed-on: https://go-review.googlesource.com/8898
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
diff --git a/src/runtime/sys_plan9_386.s b/src/runtime/sys_plan9_386.s
index b9db8cb..cae326a 100644
--- a/src/runtime/sys_plan9_386.s
+++ b/src/runtime/sys_plan9_386.s
@@ -52,7 +52,7 @@
 	MOVL	$-1, ret_hi+20(FP)
 	RET
 
-TEXT runtime·close(SB),NOSPLIT,$0
+TEXT runtime·closefd(SB),NOSPLIT,$0
 	MOVL	$4, AX
 	INT	$64
 	MOVL	AX, ret+4(FP)