syscall: correct CertOpenStore to expect a 0 return value on failure

According to [1], this function returns NULL when it errors, rather than
INVALID_HANDLE_VALUE, which other Win32 functions return. This was
pointed out in CL 273446 for the x/sys package, and this patch here
cleans it up for the syscall package and updates the vendored x/sys
package using the usual `go get/go mod vendor` dance. The function is
currently in use by crypto/x509/root_windows.go, which calls
CertOpenStore(CERT_STORE_PROV_MEMORY), which I assume can fail under OOM
or other weird conditions. Quick reversing indicates that [1] is
correct, as there's a `xor eax, eax` in the error paths of the function
just before jumping to the epilogue.

[1] https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certopenstore#return-value

Change-Id: I77c0b0319c13313212f8710785252c494da56ed5
Reviewed-on: https://go-review.googlesource.com/c/go/+/273827


Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Trust: Alex Brainman <alex.brainman@gmail.com>