Move the dynamic loading of advapi into its own module.

There's now a winsecur.[ch], which centralises helper functions using
the Windows security stuff in advapi.h (currently just get_user_sid),
and also centralises the run-time loading of those functions and
checking they're all there.

[originally from svn r10082]

windows/winsecur.h

@@ -0,0 +1,32 @@
+/*
+ * winsecur.h: some miscellaneous security-related helper functions,
+ * defined in winsecur.c, that use the advapi32 library. Also
+ * centralises the machinery for dynamically loading that library.
+ */
+
+#if !defined NO_SECURITY
+
+#include <aclapi.h>
+
+#ifndef WINSECUR_GLOBAL
+#define WINSECUR_GLOBAL extern
+#endif
+
+DECL_WINDOWS_FUNCTION(WINSECUR_GLOBAL, BOOL, OpenProcessToken,
+		      (HANDLE, DWORD, PHANDLE));
+DECL_WINDOWS_FUNCTION(WINSECUR_GLOBAL, BOOL, GetTokenInformation,
+		      (HANDLE, TOKEN_INFORMATION_CLASS,
+                       LPVOID, DWORD, PDWORD));
+DECL_WINDOWS_FUNCTION(WINSECUR_GLOBAL, BOOL, InitializeSecurityDescriptor,
+		      (PSECURITY_DESCRIPTOR, DWORD));
+DECL_WINDOWS_FUNCTION(WINSECUR_GLOBAL, BOOL, SetSecurityDescriptorOwner,
+		      (PSECURITY_DESCRIPTOR, PSID, BOOL));
+DECL_WINDOWS_FUNCTION(WINSECUR_GLOBAL, DWORD, GetSecurityInfo,
+		      (HANDLE, SE_OBJECT_TYPE, SECURITY_INFORMATION,
+		       PSID *, PSID *, PACL *, PACL *,
+		       PSECURITY_DESCRIPTOR *));
+
+int got_advapi(void);
+PSID get_user_sid(void);
+
+#endif