Fix archive writer

1. align to even address
2. Fix the use of GElf_Ehdr and Elf32_Ehdr
3. Fix the header related
RA format support for rtems-ld

1. Automatically place object files in archive files into a ra file,
   using new option --runtime-lib
2. Add a new option --one-file to decide whether the collected
   object files should be merged into the rap file or not.

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Ignore common section and null(index 0) section

Signed-off-by: Peng Fan <van.freenix@gmail.com>
Implement a new tool 'rtems-ra'

rtems-ra supports converting an elf archive file into a rap archive file.
It also support add, replace and delete rap files from the rap archive
file.