packagefs: ReadAttribute with user_memcpy().

Fix various 64 bit related warnings

Mostly printf() format strings and signed-unsigned comparisons.
Fixes the x86_64 build.

packagefs: Add automatic SYS:PACKAGE_FILE attribute

* Rename SYS:PACKAGE attribute to SYS:PACKAGE_FILE.
* Re-add SYS:PACKAGE attribute. It contains the versioned name of the
package.

packagefs: Share string instances globally

Introduce a class String which refers to shared private data that is
registered in a global hash table (in class StringPool) and use the
class consequently. This eliminates duplicate allocations for the same
string and also speeds up tests for equality. There's quite a bit
overhead for the management structures (apparently even more than for
the string data itself), but due to almost all strings being used
multiple times this still almost halves the memory usage for string
data.

packagefs: Organize sources into subdirectories

Fix various 64 bit related warnings

Mostly printf() format strings and signed-unsigned comparisons.
Fixes the x86_64 build.

packagefs: Add automatic SYS:PACKAGE_FILE attribute

* Rename SYS:PACKAGE attribute to SYS:PACKAGE_FILE.
* Re-add SYS:PACKAGE attribute. It contains the versioned name of the
package.

packagefs: Share string instances globally

Introduce a class String which refers to shared private data that is
registered in a global hash table (in class StringPool) and use the
class consequently. This eliminates duplicate allocations for the same
string and also speeds up tests for equality. There's quite a bit
overhead for the management structures (apparently even more than for
the string data itself), but due to almost all strings being used
multiple times this still almost halves the memory usage for string
data.

packagefs: Organize sources into subdirectories