Add a process spawn syscall and use it to start a proc.

Also add a skeleton VirtualMemory manager to be used per process.

zion/include/zcall.h

@@ -3,6 +3,17 @@
 #include <stdint.h>
 
 #define Z_THREAD_EXIT 0x01
+
+#define Z_PROCESS_SPAWN 0x10
+
 #define Z_DEBUG_PRINT 0x100
 
 uint64_t ZDebug(const char* message);
+
+// TODO: Move structs into an internal header.
+struct ZProcessSpawnReq {
+  uint64_t elf_base;
+  uint64_t elf_size;
+};
+
+uint64_t ZProcessSpawn(uint64_t elf_base, uint64_t elf_size);