Bug 979913: Fix GCC warning about undeclared function |snprintf|, r=khuey
Bug 979913: Conditionally define PAGE_SIZE, r=khuey

With this patch the PAGE_SIZE value from the system is used if
possible. If page size is not defined by the system, it is set
to 4096 bytes and a warning is emitted. PAGE_ALIGN_MASK is now
derived from PAGE_SIZE. With these changes, the code should be
more robust on systems with non-4KiB page size.
Bug 979913: Remove unused variables, r=khuey