xseg: Add X_UPDATE op
xseg_posixfd: Change fifo permissions

Make sure the pipes that are created, are readable/writable by the group of the
process that creates them.
xseg: Fix permissions of the logfile

Make sure that the new logfiles are readable and writable by the group of the
process that creates them.
xlock: Add 'xlock_' prefix to {pack, unpack}_owner
xseg-tool: Fix recoverlocks functionality
xseg-tool: Fix verify functionality
xseg_posixfd: Add S_ISGID bit to fifo's directory

Add S_ISGID bit to fifo's directory. This way each fifo created under this
directory inherits the group id of the POSIXFD directory. This enables different
Archipelago components to signal each other independently from their effective
user id.
xseg: Do not create posixfd directory

Do not implicitly create posixfd directory. Instead, expect it to be already
setup correctly and return an error otherwise.
xlock: Replace label-based PC with asm-based

Replace getting the current program counter from labels, since it may break with
different optimization settings. Since the previous implementations could be
greatly influenced by the compiler's behavior, switch to an assembly-based
approach.
xseg-tool: Handle keyboard interrupt
xseg_posix: Propagate errno of segment ops

Propagate errno when calling an operation on the 'posix' segment type.
xseg_posixfd: Remove 'posixfd' segment type

Remove 'posixfd' segment type. This segment type was identical to 'posix' type
and posed no added benefit. Moreover, it was never used by any xseg or
Archipelago componenent.
xseg: Propagate errno for xseg_join

Propagate the correct errno to the caller of xseg_join function.
xseg: Create all log files with 777 and rely on umask
xseg_posixfd: Remove umask and make fifo mode 666

Remove umask calls and make fifo mode 666. This way, we avoid calling umask from
the librar and we rely on the umask of each process in order to create the pipes
with the right permissions.
xseg: Make XSEGLOG log to stderr
Merge pull request #19 from philipgian/release-0.4

Various libxeg improvements