throw.h: simplified a compilation conditional.
#ifndef MRB_THROW_H
#define MRB_THROW_H
-#if defined(MRB_USE_CXX_ABI)
-# if !defined(__cplusplus)
+#if defined(MRB_USE_CXX_ABI) && !defined(__cplusplus)
# error Trying to use C++ exception handling in C code
#endif
-#endif
#if defined(MRB_USE_CXX_EXCEPTION)
