Add rust bpf allocator (#4426)

programs/bpf_loader/src/alloc.rs

@@ -0,0 +1,17 @@
+use std::alloc::Layout;
+use std::fmt;
+
+/// Based loosely on the unstable std::alloc::Alloc trait
+pub trait Alloc {
+    fn alloc(&mut self, layout: Layout) -> Result<*mut u8, AllocErr>;
+    fn dealloc(&mut self, ptr: *mut u8, layout: Layout);
+}
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct AllocErr;
+
+impl fmt::Display for AllocErr {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("Error: Memory allocation failed")
+    }
+}