INT64_MIN was causing problems ('not declared'), because C99 requires some
C++-specific behavior, which C++11 prohibits...
Comments from clang's stdint implementation (http://clang.llvm.org/doxygen/stdint_8h_source.html):
// C99 7.18.3 Limits of other integer types
//
// Footnote 219, 220: C++ implementations should define these macros only when
// __STDC_LIMIT_MACROS is defined before <stdint.h> is included.
//
// Footnote 222: C++ implementations should define these macros only when
// __STDC_CONSTANT_MACROS is defined before <stdint.h> is included.
//
// C++11 [cstdint.syn]p2:
//
// The macros defined by <cstdint> are provided unconditionally. In particular,
// the symbols __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS (mentioned in
// footnotes 219, 220, and 222 in the C standard) play no role in C++.
//
// C11 removed the problematic footnotes.
