syscall: add GO_ARGS to Go-called assembly

Fixes sporadic linux/386 build failure (untyped args)
and probably some others we haven't observed yet.

Fixes #8727.

TBR=iant
R=golang-codereviews
CC=bradfitz, golang-codereviews, iant, khr, r
https://golang.org/cl/143930043

src/syscall/asm_linux_386.s

@@ -119,6 +119,7 @@ ok2:
 // func socketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, errno int)
 // Kernel interface gets call sub-number and pointer to a0.
 TEXT ·socketcall(SB),NOSPLIT,$0-36
+	GO_ARGS
 	CALL	runtime·entersyscall(SB)
 	MOVL	$SYS_SOCKETCALL, AX	// syscall entry
 	MOVL	4(SP), BX	// socket call number
@@ -143,6 +144,7 @@ oksock:
 // func rawsocketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, errno int)
 // Kernel interface gets call sub-number and pointer to a0.
 TEXT ·rawsocketcall(SB),NOSPLIT,$0-36
+	GO_ARGS
 	MOVL	$SYS_SOCKETCALL, AX	// syscall entry
 	MOVL	4(SP), BX	// socket call number
 	LEAL		8(SP), CX	// pointer to call arguments
@@ -168,6 +170,7 @@ oksock1:
 // Underlying system call is
 //	llseek(int fd, int offhi, int offlo, int64 *result, int whence)
 TEXT ·seek(SB),NOSPLIT,$0-28
+	GO_ARGS
 	CALL	runtime·entersyscall(SB)
 	MOVL	$SYS__LLSEEK, AX	// syscall entry
 	MOVL	4(SP), BX	// fd

src/syscall/asm_linux_amd64.s

@@ -116,6 +116,7 @@ ok2:
 	RET
 
 TEXT ·gettimeofday(SB),NOSPLIT,$0-16
+	GO_ARGS
 	MOVQ	8(SP), DI
 	MOVQ	$0, SI
 	MOVQ	runtime·__vdso_gettimeofday_sym(SB), AX

src/syscall/asm_linux_arm.s

@@ -111,6 +111,7 @@ ok2:
 // Underlying system call is
 //	llseek(int fd, int offhi, int offlo, int64 *result, int whence)
 TEXT ·seek(SB),NOSPLIT,$0-32
+	GO_ARGS
 	BL	runtime·entersyscall(SB)
 	MOVW	$SYS__LLSEEK, R7	// syscall entry
 	MOVW	4(SP), R0	// fd

src/syscall/asm_plan9_386.s

@@ -132,6 +132,7 @@ TEXT	·RawSyscall6(SB),NOSPLIT,$0-40
 
 //func seek(placeholder uintptr, fd int, offset int64, whence int) (newoffset int64, err string)
 TEXT ·seek(SB),NOSPLIT,$0-36
+	GO_ARGS
 	LEAL	newoffset+24(SP), AX
 	MOVL	AX, placeholder+4(SP)
 	
@@ -163,6 +164,8 @@ copyresult6:
 //func exit(code int)
 // Import runtime·exit for cleanly exiting.
 TEXT ·exit(SB),NOSPLIT,$4-4
+	GO_ARGS
+	NO_LOCAL_POINTERS
 	MOVL	code+0(FP), AX
 	MOVL	AX, 0(SP)
 	CALL	runtime·exit(SB)

src/syscall/asm_plan9_amd64.s

@@ -131,6 +131,7 @@ TEXT	·RawSyscall6(SB),NOSPLIT,$0-80
 
 //func seek(placeholder uintptr, fd int, offset int64, whence int) (newoffset int64, err string)
 TEXT ·seek(SB),NOSPLIT,$0-56
+	GO_ARGS
 	LEAQ	newoffset+40(SP), AX
 	MOVQ	AX, placeholder+8(SP)
 	
@@ -161,6 +162,8 @@ copyresult6:
 //func exit(code int)
 // Import runtime·exit for cleanly exiting.
 TEXT ·exit(SB),NOSPLIT,$8-8
+	GO_ARGS
+	NO_LOCAL_POINTERS
 	MOVQ	code+0(FP), AX
 	MOVQ	AX, 0(SP)
 	CALL	runtime·exit(SB)