IBM i compilers now predefine __PASE__. This commit updates
code to rely on that rather than manually setting (or relying on)
a _PASE definition.
PR-URL: https://github.com/libuv/libuv/pull/1782
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>