Bug 1279633 - Define AsmJSCache_MIN in terms of AsmJSCacheSuccess, instead of the other way around; r=till

rust-bindgen will make an enum variant for the first definition it encounters,
and then define duplicates as constants outside of the enum definition. This has
the unfortunate effect of making AsmJSCache_MIN an enum variant and
AsmJSCache_Success the constant definition outside of the enum in the case of
the AsmJSCacheResult enumeration. This commit rectifies that.

This upstreams the following commit from servo/mozjs:

    50f47cf Bind AsmJSCache_Success rather than AsmJSCache_MIN

js/src/jsapi.h

@@ -5710,8 +5710,8 @@ typedef void
 /** The list of reasons why an asm.js module may not be stored in the cache. */
 enum AsmJSCacheResult
 {
-    AsmJSCache_MIN,
-    AsmJSCache_Success = AsmJSCache_MIN,
+    AsmJSCache_Success,
+    AsmJSCache_MIN = AsmJSCache_Success,
     AsmJSCache_ModuleTooSmall,
     AsmJSCache_SynchronousScript,
     AsmJSCache_QuotaExceeded,