libelf: Make sure elf_getdata_rawchunk returns aligned data.

libelf: Make sure elf_getdata_rawchunk returns aligned data.

elf_getdata_rawchunk might return an unaligned buffer for the requested
ELF data type. Make sure the data is also correctly aligned when using
an mmapped file. Also add some missing alignments for ELF data types
for __libelf_type_align (the missing types could also make elf_getdata
to return unaligned data).

Signed-off-by: Mark Wielaard <mjw@redhat.com>