Add pre-built PRoot manual page to sources.

That way, there's no need to generate it again when creating a
package.
Fix a couple of portability issues.
Re-enable heap emulation support on x86.

This support was historically disabled because it exposes a serious
problem (all tests fail) on http://build.opensuse.org.  After some
tests, this problem appears only on some [AMD processors, hypervisors]
couples.  I was not able to investigate this AMD/hypervisor/heap bug
correctly (no remote shell on build.opensuse.org), and the heap
emulation support is required when ASLR is disabled (as it's now the
case), so I re-enable it.  With luck (hum!), no one will ever hit this
bug.
Update PRoot's roadmap & changelog.
Revert "Make pop_component() return removed component".

Quote: The function pop_component in PRoot's path/path.c doesn't seem
       to correctly handle the case when the path argument has only
       one component, say "/usr".  I can't figure out what the right
       thing to do in this case is, though: it seems like you would
       both want to leave the string as "/" and return "usr" as the
       last component, but there's no placement of a \0 byte that
       would have that effect.  When the component is of length 2 or
       more, it seems like only the return address is affected: For
       instance on "/usr" it will set the string to "/" and return
       "sr" instead of "usr".  But in the further corner case where
       the first component is only one character long, the assertion
       "assert(offset + 1 < length)" will fail causing PRoot to
       terminate.

       -- Stephen McCamant https://github.com/cedric-vincent/PRoot/issues/59

Reported-by: Stephen McCamant <mccamant@cs.umn.edu>
Investigated-by: Stephen McCamant <mccamant@cs.umn.edu>
Fix a couple of portability issues, again.
Fix a memory corruption in a test.
Prepare release of PRoot v4.0.0.
Don't canonicalize named file descriptors that reference special objects.

Named file descriptors may reference special objects like pipes,
sockets, inodes, ...  Such objects do not belong to the file-system.
Relax some assertions in ptrace emulation support.