[project] Generate syscalls from new interface DSL

This change adds a new interface DSL for specifying objects (with
methods) and interfaces (that expose objects, and optionally have their
own methods).

Significant changes:

- Add the new scripts/definitions Python module to parse the DSL
- Add the new definitions directory containing DSL definition files
- Use cog to generate syscall-related code in kernel and libj6
- Unify ordering of pointer + length pairs in interfaces

definitions/objects/system.def

@@ -0,0 +1,29 @@
+import "objects/endpoint.def"
+import "objects/vma.def"
+
+# The system object represents a handle to kernel functionality
+# needed by drivers and other priviledged services
+object system : kobject {
+    uid fa72506a2cf71a30
+
+    # Get a log line from the kernel log
+    method get_log {
+        param buffer buffer [out]   # Buffer for the log message data structure
+    }
+
+    # Ask the kernel to send this process messages whenever
+    # the given IRQ fires
+    method bind_irq {
+        param dest object endpoint  # Endpoint that will receive messages
+        param irq uint              # IRQ number to bind
+    }
+
+    # Create a VMA and map an area of physical memory into it,
+    # also mapping that VMA into the current process
+    method map_phys {
+        param area object vma [out] # Receives a handle to the VMA created
+        param phys address          # The physical address of the area
+        param size size             # Size of the area, in pages
+        param flags uint32          # Flags to apply to the created VMA
+    }
+}