[kernel] Make channels stream based

Multiple changes regarding channels. Mainly channels are now stream
based and can handle partial reads or writes. Channels now use the
kernel buffers area with the related buffer_cache. Added a fake stdout
stream channel and kernel task to read its contents to the screen in
preparation for handing channels as stdin/stdout to processes.

src/libraries/kutil/include/kutil/vm_space.h

@@ -22,8 +22,10 @@ struct vm_range
 	vm_state state;
 
 	inline uintptr_t end() const { return address + size; }
-	inline int compare(const vm_range *other) const {
-		return other->address - address;
+	inline int64_t compare(const vm_range *other) const {
+		if (address > other->address) return -1;
+		else if (address < other->address) return 1;
+		else return 0;
 	}
 };
 

src/libraries/kutil/vm_space.cpp

@@ -253,7 +253,7 @@ vm_space::commit(uintptr_t start, size_t size)
 vm_state
 vm_space::get(uintptr_t addr)
 {
-	node_type *node = find_overlapping(m_ranges.root(), addr, 0);
+	node_type *node = find_overlapping(m_ranges.root(), addr, 1);
 	return node ? node->state : vm_state::unknown;
 }