librclone/ctest: add Windows support and fix memory management

Make ctest build and run on Windows in addition to Linux/macOS:

- Add OS detection in Makefile using ifeq ($(OS),Windows_NT)
- Use .lib extension and .exe suffix on Windows
- Link Windows system libraries (winmm, ws2_32, ole32)
- Remove unused dlfcn.h include that prevented compilation on Windows

Fix memory management to use RcloneFreeString instead of free for
strings returned by RcloneRPC, as documented in the librclone README.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

librclone/ctest/Makefile

@@ -1,17 +1,26 @@
 CFLAGS = -g -Wall
-LDFLAGS = -L. -lrclone -lpthread -ldl
 
-ctest: ctest.o librclone.a
+ifeq ($(OS),Windows_NT)
+EXE = .exe
+LIB = librclone.lib
+LDFLAGS = -L. -lrclone -lwinmm -lws2_32 -lole32
+else
+EXE =
+LIB = librclone.a
+LDFLAGS = -L. -lrclone -lpthread -ldl
+endif
+
+ctest$(EXE): ctest.o $(LIB)
 	$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
 
 ctest.o: ctest.c librclone.h
 	$(CC) $(CFLAGS) -c $^ $(LDFLAGS)
 
-librclone.a librclone.h:
-	go build --buildmode=c-archive -o librclone.a github.com/rclone/rclone/librclone
+$(LIB) librclone.h:
+	go build --buildmode=c-archive -o $(LIB) github.com/rclone/rclone/librclone
 
-test:	ctest
-	./ctest
+test:	ctest$(EXE)
+	./ctest$(EXE)
 
 clean:
-	rm -f tmp ctest *.o *.a *.h *.gch
+	rm -f tmp ctest ctest.exe *.o *.a *.lib *.h *.gch

librclone/ctest/ctest.c

@@ -4,14 +4,13 @@ This is a very simple test/demo program for librclone's C interface
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <dlfcn.h>
 #include "librclone.h"
 
 void testRPC(char *method, char *in) {
     struct RcloneRPCResult out = RcloneRPC(method, in);
     printf("status: %d\n", out.Status);
     printf("output: %s\n", out.Output);
-    free(out.Output);
+    RcloneFreeString(out.Output);
 }
 
 // noop command
@@ -44,7 +43,7 @@ void testNoOp() {
         fprintf(stderr, "Wrong status: want: %d: got: %d\n", 200, out.Status);
         exit(EXIT_FAILURE);
     }
-    free(out.Output);
+    RcloneFreeString(out.Output);
 }
 
 // error command
@@ -83,7 +82,7 @@ void testError() {
         fprintf(stderr, "Wrong status: want: %d: got: %d\n", 500, out.Status);
         exit(EXIT_FAILURE);
     }
-    free(out.Output);
+    RcloneFreeString(out.Output);
 }
 
 // copy file using "operations/copyfile" command