Initial changes to remove /boot/common

* find_directory() and hard-coded paths use /boot/system instead of
  /boot/common.
* The build system creates the writable directories in /boot/system
  instead of /boot/common.
* The build system no longer installs any packages in /boot/common.
runtime loader: 64-bit ktrace output fixes
Remove /boot/common for good

* Remove support for the "common" installation location from packagefs,
  package kit, package daemon, package managers.
* Rename the B_COMMON_*_DIRECTORY constants referring to writable
  directories to B_SYSTEM_*_DIRECTORY.
* Remove/adjust the use of various B_COMMON_*_DIRECTORY constants.
  I'm sure some occurrence still remain. They can be adjusted when the
  remaining B_COMMON_*_DIRECTORY constants are removed.
Update packages that hard-coded references to /boot/common

There are a few more (like gcc still including there respective search
paths), but those should be harmless and can be adjusted later.
Declare libicu* requirements in the haiku* packages
Make secondary haiku_devel package depend on the primary

Only the primary haiku_devel package contains the system headers.
Fix incorrect uses of getpwuid_r()

The function's behavior was recently fixed to succeed, but return a NULL
pointer, when the entry was not found. Fixes a crash in this case.