Two small fixes to fix compiler errors on Mac OSX

I was not able to compiler on Mac OSX, so I fixed the compiler issues.

The default for _SC_PAGE_SIZE was taken from my /usr/include/unistd.h.

Compiler version:

Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.2
Thread model: posix