Pull sync generated syscalls

This moves all the current users of
$GOROOT/src/syscall/mksyscall_windows.go to instead use
golang.org/x/sys/windows/mkwinsyscall, as directed by the version of the
former in Go 1.15.

It also syncs the local forks of mksyscall_windows.go with the latest
version of golang.org/x/sys/windows/mkwinsyscall/mkwinsyscall.go, so
that the local patches can be easily seen in a side-by-side comparison.
Significant changes compared to the in-tree forked versions:
* *bool parameters are read back through a temp-var, not directly like
  other pointer parameters.
* ?-suffixed function names support testing for function presence before
  calling. This replaces a local implementation of this in
  pkg/security, which was not actually used anyway. The upstream version
  correctly supports functions that don't already have an error return.
* `errnoErr(0)` is now useful, so each call of `errnoErr` doesn't need
  to be protected with a check for 0 first.
* The generated functions are now sorted. This of course produced a
  *lot* of churn in the generated files.

vhd\vhd.go was changed to generate syscalls into zvhd_windows.go, since
regeneration removes the build tag added by hand in
9d8277341f.

After all that, I also ran
```
go generate . .\pkg\etw\ .\pkg\process\ .\pkg\security\ .\vhd\
```
to update all the existing generated code.

Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>

pkg/process/syscall.go

@@ -6,7 +6,7 @@ import (
 	"golang.org/x/sys/windows"
 )
 
-//go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zsyscall_windows.go syscall.go
+//go:generate go run golang.org/x/sys/windows/mkwinsyscall -output zsyscall_windows.go syscall.go
 
 //sys enumProcesses(pids *uint32, bufferSize uint32, retBufferSize *uint32) (err error) = kernel32.K32EnumProcesses
 //sys getProcessMemoryInfo(process handle, memCounters *ProcessMemoryCountersEx, size uint32) (err error) = kernel32.K32GetProcessMemoryInfo

pkg/process/zsyscall_windows.go

@@ -19,6 +19,7 @@ const (
 
 var (
 	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
 )
 
 // errnoErr returns common boxed Errno values, to prevent
@@ -26,7 +27,7 @@ var (
 func errnoErr(e syscall.Errno) error {
 	switch e {
 	case 0:
-		return nil
+		return errERROR_EINVAL
 	case errnoERROR_IO_PENDING:
 		return errERROR_IO_PENDING
 	}
@@ -47,11 +48,7 @@ var (
 func enumProcesses(pids *uint32, bufferSize uint32, retBufferSize *uint32) (err error) {
 	r1, _, e1 := syscall.Syscall(procK32EnumProcesses.Addr(), 3, uintptr(unsafe.Pointer(pids)), uintptr(bufferSize), uintptr(unsafe.Pointer(retBufferSize)))
 	if r1 == 0 {
-		if e1 != 0 {
-			err = errnoErr(e1)
-		} else {
-			err = syscall.EINVAL
-		}
+		err = errnoErr(e1)
 	}
 	return
 }
@@ -59,11 +56,7 @@ func enumProcesses(pids *uint32, bufferSize uint32, retBufferSize *uint32) (err
 func getProcessMemoryInfo(process handle, memCounters *ProcessMemoryCountersEx, size uint32) (err error) {
 	r1, _, e1 := syscall.Syscall(procK32GetProcessMemoryInfo.Addr(), 3, uintptr(process), uintptr(unsafe.Pointer(memCounters)), uintptr(size))
 	if r1 == 0 {
-		if e1 != 0 {
-			err = errnoErr(e1)
-		} else {
-			err = syscall.EINVAL
-		}
+		err = errnoErr(e1)
 	}
 	return
 }
@@ -71,11 +64,7 @@ func getProcessMemoryInfo(process handle, memCounters *ProcessMemoryCountersEx,
 func queryFullProcessImageName(process handle, flags uint32, buffer *uint16, bufferSize *uint32) (err error) {
 	r1, _, e1 := syscall.Syscall6(procQueryFullProcessImageNameW.Addr(), 4, uintptr(process), uintptr(flags), uintptr(unsafe.Pointer(buffer)), uintptr(unsafe.Pointer(bufferSize)), 0, 0)
 	if r1 == 0 {
-		if e1 != 0 {
-			err = errnoErr(e1)
-		} else {
-			err = syscall.EINVAL
-		}
+		err = errnoErr(e1)
 	}
 	return
 }