libdpkg: Remove unused fd_buf_copy()

This function is not really needed once we have fd_read(), it also
performs some slight unneeded work.

lib/dpkg/buffer.c

@@ -99,10 +99,6 @@ buffer_write(struct buffer_data *data, const void *buf, off_t length)
 	off_t ret = length;
 
 	switch (data->type) {
-	case BUFFER_WRITE_BUF:
-		memcpy(data->arg.ptr, buf, length);
-		data->arg.ptr += length;
-		break;
 	case BUFFER_WRITE_VBUF:
 		varbufaddbuf((struct varbuf *)data->arg.ptr, buf, length);
 		break;

lib/dpkg/buffer.h

@@ -30,7 +30,6 @@
 
 DPKG_BEGIN_DECLS
 
-#define BUFFER_WRITE_BUF		0
 #define BUFFER_WRITE_VBUF		1
 #define BUFFER_WRITE_FD			2
 #define BUFFER_WRITE_NULL		3
@@ -55,9 +54,6 @@ struct buffer_data {
 # define fd_fd_copy(fd1, fd2, limit, ...) \
 	buffer_copy_IntInt(fd1, BUFFER_READ_FD, fd2, BUFFER_WRITE_FD, \
 	                   limit, __VA_ARGS__)
-# define fd_buf_copy(fd, buf, limit, ...) \
-	buffer_copy_IntPtr(fd, BUFFER_READ_FD, buf, BUFFER_WRITE_BUF, \
-	                   limit, __VA_ARGS__)
 # define fd_vbuf_copy(fd, buf, limit, ...) \
 	buffer_copy_IntPtr(fd, BUFFER_READ_FD, buf, BUFFER_WRITE_VBUF, \
 	                   limit, __VA_ARGS__)