Reorganize the C API headers to improve build times.

Type specific declarations have been moved to Type.h and error handling
routines have been moved to ErrorHandling.h. Both are included in Core.h
so nothing should change for projects directly including the headers,
but transitive dependencies may be affected.

llvm-svn: 255965
diff --git a/llvm/tools/llvm-c-test/object.c b/llvm/tools/llvm-c-test/object.c
index a5421d9..4352178 100644
--- a/llvm/tools/llvm-c-test/object.c
+++ b/llvm/tools/llvm-c-test/object.c
@@ -13,6 +13,7 @@
 \*===----------------------------------------------------------------------===*/
 
 #include "llvm-c-test.h"
+#include "llvm-c/Core.h"
 #include "llvm-c/Object.h"
 #include <stdio.h>
 #include <stdlib.h>