Fixed compilation on recent Ubuntu versions (12.04 and higher) and Clang 3.3

Corrected rect variable wrongly initialized with itself (fix #1)

Added missing XCBStringFromRect() use in a formatted string.

Updated XCBKit GNUmakefile to use pkg-config to get the linked XCB libraries
(starting with Ubuntu 12.04 xcb-event package is now part of xcb-util)

Note: Turned off Workspace subproject that requires some serious rewriting due
to API changes in EtoileUI.