Protect possibly predefined preprocessor symbol
Protect possibly predefined preprocessor symbol

On my systems (RHEL7 and Android Termux) PAGE_SIZE is defined to 4096 in /usr/include/sys/user.h .  The enum then produces a compile-term error.
Adding this change resolves this error for me.

root-mirror/cling,karies/cling,root-mirror/cling,root-mirror/cling,karies/cling,karies/cling,karies/cling,root-mirror/cling,root-mirror/cling,karies/cling,root-mirror/cling,karies/cling