w64: Don't redefine lseek, ftruncate

MinGW-w64 already defines lseek and ftruncate (and uses the 64 bit
variants). The conditional compilation avoids redefinitions
(which would be wrong) and compiler warnings.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

qemu-common.h

@@ -93,9 +93,13 @@ typedef int (*fprintf_function)(FILE *f, const char *fmt, ...)
 
 #ifdef _WIN32
 #define fsync _commit
-#define lseek _lseeki64
+#if !defined(lseek)
+# define lseek _lseeki64
+#endif
 int qemu_ftruncate64(int, int64_t);
-#define ftruncate qemu_ftruncate64
+#if !defined(ftruncate)
+# define ftruncate qemu_ftruncate64
+#endif
 
 static inline char *realpath(const char *path, char *resolved_path)
 {