all: single space after period.

The tree's pretty inconsistent about single space vs double space
after a period in documentation. Make it consistently a single space,
per earlier decisions. This means contributors won't be confused by
misleading precedence.

This CL doesn't use go/doc to parse. It only addresses // comments.
It was generated with:

$ perl -i -npe 's,^(\s*// .+[a-z]\.)  +([A-Z]),$1 $2,' $(git grep -l -E '^\s*//(.+\.)  +([A-Z])')
$ go test go/doc -update

Change-Id: Iccdb99c37c797ef1f804a94b22ba5ee4b500c4f7
Reviewed-on: https://go-review.googlesource.com/20022
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Dave Day <djd@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s
index 9237d57..2d16f49 100644
--- a/src/runtime/asm_386.s
+++ b/src/runtime/asm_386.s
@@ -226,7 +226,7 @@
 
 // func mcall(fn func(*g))
 // Switch to m->g0's stack, call fn(g).
-// Fn must never return.  It should gogo(&g->sched)
+// Fn must never return. It should gogo(&g->sched)
 // to keep running g.
 TEXT runtime·mcall(SB), NOSPLIT, $0-4
 	MOVL	fn+0(FP), DI
@@ -259,7 +259,7 @@
 	RET
 
 // systemstack_switch is a dummy routine that systemstack leaves at the bottom
-// of the G stack.  We need to distinguish the routine that
+// of the G stack. We need to distinguish the routine that
 // lives at the bottom of the G stack from the one that lives
 // at the top of the system stack because the one at the top of
 // the system stack terminates the stack walk (see topofstack()).
@@ -291,7 +291,7 @@
 	CALL	AX
 
 switch:
-	// save our state in g->sched.  Pretend to
+	// save our state in g->sched. Pretend to
 	// be systemstack_switch if the G stack is scanned.
 	MOVL	$runtime·systemstack_switch(SB), (g_sched+gobuf_pc)(AX)
 	MOVL	SP, (g_sched+gobuf_sp)(AX)
@@ -900,7 +900,7 @@
 	RET
 
 endofpage:
-	// address ends in 1111xxxx.  Might be up against
+	// address ends in 1111xxxx. Might be up against
 	// a page boundary, so load ending at last byte.
 	// Then shift bytes down using pshufb.
 	MOVOU	-32(AX)(BX*1), X1
@@ -1145,7 +1145,7 @@
 
 GLOBL masks<>(SB),RODATA,$256
 
-// these are arguments to pshufb.  They move data down from
+// these are arguments to pshufb. They move data down from
 // the high bytes of the register to the low bytes of the register.
 // index is how many bytes to move.
 DATA shifts<>+0x00(SB)/4, $0x00000000
@@ -1370,7 +1370,7 @@
 	MOVL	(SI), SI
 	JMP	si_finish
 si_high:
-	// address ends in 111111xx.  Load up to bytes we want, move to correct position.
+	// address ends in 111111xx. Load up to bytes we want, move to correct position.
 	MOVL	-4(SI)(BX*1), SI
 	SHRL	CX, SI
 si_finish:
@@ -1606,7 +1606,7 @@
 TEXT runtime·prefetchnta(SB),NOSPLIT,$0-4
 	RET
 
-// Add a module's moduledata to the linked list of moduledata objects.  This
+// Add a module's moduledata to the linked list of moduledata objects. This
 // is called from .init_array by a function generated in the linker and so
 // follows the platform ABI wrt register preservation -- it only touches AX,
 // CX (implicitly) and DX, but it does not follow the ABI wrt arguments: