Check for a set_data method in elfc_phdr_write() before calling it.
Fix an off-by-one when checking if a range is in the pelf file.

To preserve the PT_LOAD notes with size that fits in an Elf32_Word, also
require that two pages in the physical dump be from the same segment to
combine them.
Use the page size from velf_page_handler() rather than a hard-coded value.
Modify the phdr routine to take Xwords for filesz and memsz

They can be 64-bit on 64-bit systems, so make sure we can handle it.