process: add a space allocator for the 'dynamic' part of the virtual address space, if it exists.

On x86_64, this means mmaps without a fixed address (ie, mmap(0...) ) will end up above the 4GB mark. This fixes an issue in libload where the first mmap() gets overridden by the first program header.
preloadd: GCC version and architecture has changed, update paths (bleh)
posix: remove entirely useless code from chdir()