Remove osloader.c and replace with a prep_segment() that uses userptr_t

and get_memmap() in image/segment.c

src/include/gpxe/segment.h

@@ -0,0 +1,15 @@
+#ifndef _GPXE_SEGMENT_H
+#define _GPXE_SEGMENT_H
+
+/**
+ * @file
+ *
+ * Executable image segments
+ *
+ */
+
+#include <gpxe/uaccess.h>
+
+extern int prep_segment ( userptr_t segment, size_t filesz, size_t memsz );
+
+#endif /* _GPXE_SEGMENT_H */