Dynamically allocate soinfo-structs in linker

Request memory from the system when needed instead of having a fixed
array for soinfo structs. Note that malloc() et al can't be used in
linker, so use mmap() instead.

NOT MBQs edit. I got this from: Magnus Malmborn (Change-Id: Ia77e6a835db0f4a0bfeccc4a6610b857459fd437)