Remove the ASTContext parameter from the attribute-related methods of Decl.
The implementations of these methods can Use Decl::getASTContext() to get the ASTContext.

This commit touches a lot of files since call sites for these methods are everywhere.
I used pre-tokenized "carbon.h" and "cocoa.h" headers to do some timings, and there was no real time difference between before the commit and after it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@74501 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index e99217e..b7ab863 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -903,7 +903,7 @@
             continue;
         }
 
-        if ((*I)->getAttr<OverloadableAttr>(Context)) {
+        if ((*I)->getAttr<OverloadableAttr>()) {
           // If this declaration has the "overloadable" attribute, we
           // might have a set of overloaded functions.