Don't reference the __cxxabiv1 namespace before it is defined

Referencing a namespace before it is defined currently causes compiler
errors on clang.r
It is likely to also break future versions of gcc.

Change-Id: I0d63078d684db004586f132a60186f43d4def768
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>
diff --git a/include/cxxabi.h b/include/cxxabi.h
index 3bd8a58..516e6a8 100644
--- a/include/cxxabi.h
+++ b/include/cxxabi.h
@@ -31,8 +31,6 @@
 
 #include <typeinfo>
 
-namespace abi = __cxxabiv1;
-
 namespace __cxxabiv1
 {
   extern "C" void __cxa_pure_virtual();
@@ -179,5 +177,7 @@
   };
 }
 
+namespace abi = __cxxabiv1;
+
 #endif /* defined(__GABIXX_CXXABI_H__) */