Rename memory instructions; Rework constant handling (#177)

* Rename memory instructions as proposed by the bulk-memory-operations spec.
* Rename memory manager functions to memory.* as well
* Remove automatic inlining of constant globals (Binaryen does this now)
* Improve 'const' enum compatibility
* Improve module-level export generation
* Enable the inline decorator for constant variables
* Add ERROR, WARNING and INFO macros that emit a user-defined diagnostic
* Reintroduce builtin decorator so these can appear anywhere in stdlib again
* Inline isNaN and isFinite by default
* Make an interface around gc.* similar to memory.*
* Emit an error when trying to inline a mutable variable
* Slim down CI stages
* Add a more convenient tracing utility for debugging
* Implement some prequesites for an eventual bundled GC

std/assembly/gc.ts

@@ -0,0 +1,28 @@
+@builtin export declare function iterateRoots(fn: (ref: usize) => void): void; // tslint:disable-line
+
+export namespace gc {
+
+  export function allocate(size: usize, visitFn: (ref: usize) => void): usize {
+    if (isDefined(__gc_allocate)) return __gc_allocate(size, visitFn); // tslint:disable-line
+    WARNING("Calling 'gc.allocate' requires a garbage collector to be present.");
+    return <usize>unreachable();
+  }
+
+  export function collect(): void {
+    if (isDefined(__gc_collect)) { __gc_collect(); return; } // tslint:disable-line
+    WARNING("Calling 'gc.collect' requires a garbage collector to be present.");
+    unreachable();
+  }
+
+  export function link(parentRef: usize, childRef: usize): void {
+    if (isDefined(__gc_link)) { __gc_link(parentRef, childRef); return; } // tslint:disable-line
+    WARNING("Calling 'gc.link' requires a garbage collector to be present.");
+    unreachable();
+  }
+
+  export function mark(ref: usize): void {
+    if (isDefined(__gc_mark)) { __gc_mark(ref); return; } // tslint:disable-line
+    WARNING("Calling 'gc.mark' requires a garbage collector to be present.");
+    unreachable();
+  }
+}