windows: export getProcessEntry

This function is currently copied in github.com/inconshreveable/mousetrap,
which is widely used in projects (commonly as dependency for spf13/cobra).

Until recently, mousetrap had code for backward-compatibility with old Go
versions, but now that that code was removed, it's a very small wrapper
around getProcessEntry. Exporting this function allows it to be an even
smaller wrapper (most projects would already have golang.org/x/sys as
dependency in some form or another).

windows/syscall_windows.go

@@ -1390,7 +1390,7 @@ func FindNextFile(handle Handle, data *Win32finddata) (err error) {
 	return
 }
 
-func getProcessEntry(pid int) (*ProcessEntry32, error) {
+func GetProcessEntry(pid int) (*ProcessEntry32, error) {
 	snapshot, err := CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0)
 	if err != nil {
 		return nil, err
@@ -1413,7 +1413,7 @@ func getProcessEntry(pid int) (*ProcessEntry32, error) {
 }
 
 func Getppid() (ppid int) {
-	pe, err := getProcessEntry(Getpid())
+	pe, err := GetProcessEntry(Getpid())
 	if err != nil {
 		return -1
 	}