windows: add Global{Alloc,Free}

Reference:
https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-globalalloc
https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-globalfree

Author: 0xced

windows/syscall_windows.go

@@ -364,6 +364,8 @@ func NewCallbackCDecl(fn interface{}) uintptr {
 //sys	SetCommTimeouts(handle Handle, timeouts *CommTimeouts) (err error)
 //sys	GetActiveProcessorCount(groupNumber uint16) (ret uint32)
 //sys	GetMaximumProcessorCount(groupNumber uint16) (ret uint32)
+//sys	GlobalFree(hmem Handle) (handle Handle, err error) [failretval!=0]
+//sys	GlobalAlloc(flags uint32, length uint32) (ptr uintptr, err error)
 
 // Volume Management Functions
 //sys	DefineDosDevice(flags uint32, deviceName *uint16, targetPath *uint16) (err error) = DefineDosDeviceW

windows/types_windows.go

@@ -3174,3 +3174,12 @@ type ModuleInfo struct {
 }
 
 const ALL_PROCESSOR_GROUPS = 0xFFFF
+
+// Constants for GlobalAlloc flags.
+const (
+	GMEM_FIXED    = 0x0
+	GMEM_MOVEABLE = 0x2
+	GMEM_ZEROINIT = 0x40
+	GHND          = GMEM_MOVEABLE | GMEM_ZEROINIT
+	GPTR          = GMEM_FIXED | GMEM_ZEROINIT
+)