Rename most of the platform source files.

This gets rid of all those annoying 'win', 'ux' and 'gtk' prefixes
which made filenames annoying to type and to tab-complete. Also, as
with my other recent renaming sprees, I've taken the opportunity to
expand and clarify some of the names so that they're not such cryptic
abbreviations.

windows/security-api.h

@@ -0,0 +1,49 @@
+/*
+ * security-api.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.
+ */
+
+#include <aclapi.h>
+
+/*
+ * Functions loaded from advapi32.dll.
+ */
+DECL_WINDOWS_FUNCTION(extern, BOOL, OpenProcessToken,
+                      (HANDLE, DWORD, PHANDLE));
+DECL_WINDOWS_FUNCTION(extern, BOOL, GetTokenInformation,
+                      (HANDLE, TOKEN_INFORMATION_CLASS,
+                       LPVOID, DWORD, PDWORD));
+DECL_WINDOWS_FUNCTION(extern, BOOL, InitializeSecurityDescriptor,
+                      (PSECURITY_DESCRIPTOR, DWORD));
+DECL_WINDOWS_FUNCTION(extern, BOOL, SetSecurityDescriptorOwner,
+                      (PSECURITY_DESCRIPTOR, PSID, BOOL));
+DECL_WINDOWS_FUNCTION(extern, DWORD, GetSecurityInfo,
+                      (HANDLE, SE_OBJECT_TYPE, SECURITY_INFORMATION,
+                       PSID *, PSID *, PACL *, PACL *,
+                       PSECURITY_DESCRIPTOR *));
+DECL_WINDOWS_FUNCTION(extern, DWORD, SetSecurityInfo,
+                      (HANDLE, SE_OBJECT_TYPE, SECURITY_INFORMATION,
+                       PSID, PSID, PACL, PACL));
+DECL_WINDOWS_FUNCTION(extern, DWORD, SetEntriesInAclA,
+                      (ULONG, PEXPLICIT_ACCESS, PACL, PACL *));
+bool got_advapi(void);
+
+/*
+ * Find the SID describing the current user. The return value (if not
+ * NULL for some error-related reason) is smalloced.
+ */
+PSID get_user_sid(void);
+
+/*
+ * Construct a PSECURITY_DESCRIPTOR of the type used for named pipe
+ * servers, i.e. allowing access only to the current user id and also
+ * only local (i.e. not over SMB) connections.
+ *
+ * If this function returns true, then 'psd' and 'acl' will have been
+ * filled in with memory allocated using LocalAlloc (and hence must be
+ * freed later using LocalFree). If it returns false, then instead
+ * 'error' has been filled with a dynamically allocated error message.
+ */
+bool make_private_security_descriptor(
+    DWORD permissions, PSECURITY_DESCRIPTOR *psd, PACL *acl, char **error);