bpo-40190: Add support for _SC_AIX_REALMEM in sysconf (GH-19380)

diff --git a/Misc/NEWS.d/next/Library/2020-04-05-02-58-17.bpo-40190.HF3OWo.rst b/Misc/NEWS.d/next/Library/2020-04-05-02-58-17.bpo-40190.HF3OWo.rst
new file mode 100644
index 0000000..5835933
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-04-05-02-58-17.bpo-40190.HF3OWo.rst
@@ -0,0 +1 @@
+Add support for ``_SC_AIX_REALMEM`` to :func:`posix.sysconf`.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 1adca8e..345798d 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -11424,6 +11424,9 @@
 #ifdef _SC_PAGE_SIZE
     {"SC_PAGE_SIZE",    _SC_PAGE_SIZE},
 #endif
+#ifdef _SC_AIX_REALMEM
+    {"SC_AIX_REALMEM", _SC_AIX_REALMEM},
+#endif
 #ifdef _SC_PASS_MAX
     {"SC_PASS_MAX",     _SC_PASS_MAX},
 #endif