Improve makefile portability
Add search_all_sections feature

Use : ALL_SECTIONS=1 ropdumper /path/to/binary/file

This will search for ROP gadgets even in sections with no "SEC_CODE" flag.
It will search in .bss .rodata and all these kind of usually non-executable
sections.

This can be usefull in case of a non-PaX kernel which allows code execution from
any kind of memory section: heap, bss, rodata, data, stack, got etc...