Clang warns

 test/test_INT_format.h:28:26: warning: identifier after literal will
 be treated as a reserved user-defined literal suffix in C++11
 [-Wc++11-compat-reserved-user-defined-literal]
  " expression [%"KWIML_INT_PRI##PRI"],"

because the KWIML_... part is an identifier lexically immediately
following a string literal.  Add a space between the string literal
and the identifier to avoid the C++11 user-defined literal syntax.