message: Don't do a bunch of OS gymnastics. alloca.h is only for glibc, everyone else uses stdlib.h
diff: #if !defined(alloca)
  #ifdef _WIN32
  #include <malloc.h> // alloca
  -#elif (defined(__FreeBSD__) || defined(FreeBSD_kernel) || defined(__DragonFly__)) && !defined(__GLIBC__)
  -#include <stdlib.h> // alloca. FreeBSD uses stdlib.h unless GLIBC
  +#elif !defined(__GLIBC__)
  +#include <stdlib.h> // alloca
  #else
  -#include <alloca.h> // alloca
  +#include <alloca.h> // alloca. glibc has an alloca specific header
  #endif
  #endif
  