linker: New sources to manage the ELF program header table.

This patch introduces two new source files containing a set of functions
to manage the program header table in an ELF binary, including the ability
to load PT_LOAD segments, and apply PT_GNU_RELRO protection.

Note: the files are not used currently, this will appear in a series
      of future patches that will gradually modify linker.c to use
      the phdr_table_xxx functions properly.

Change-Id: Ia3d4c1ff5fc3e265d8258b64b492f4e643f51bdc
4 files changed