bpo-11233: Create availability directive for documentation (GH-9692)

Replace "Availability: xxx" with ".. availability:: xxx" in the doc.
Original patch by Georg Brandl.

Co-Authored-By: Georg Brandl <georg@python.org>
diff --git a/Doc/library/resource.rst b/Doc/library/resource.rst
index bdfe5f6..bd49c87 100644
--- a/Doc/library/resource.rst
+++ b/Doc/library/resource.rst
@@ -92,7 +92,7 @@
    :exc:`PermissionError` when the user doesn't have ``CAP_SYS_RESOURCE`` for
    the process.
 
-   Availability: Linux 2.6.36 or later with glibc 2.13 or later
+   .. availability:: Linux 2.6.36 or later with glibc 2.13 or later.
 
    .. versionadded:: 3.4
 
@@ -178,7 +178,7 @@
 
    The number of bytes that can be allocated for POSIX message queues.
 
-   Availability: Linux 2.6.8 or later.
+   .. availability:: Linux 2.6.8 or later.
 
    .. versionadded:: 3.4
 
@@ -187,7 +187,7 @@
 
    The ceiling for the process's nice level (calculated as 20 - rlim_cur).
 
-   Availability: Linux 2.6.12 or later.
+   .. availability:: Linux 2.6.12 or later.
 
    .. versionadded:: 3.4
 
@@ -196,7 +196,7 @@
 
    The ceiling of the real-time priority.
 
-   Availability: Linux 2.6.12 or later.
+   .. availability:: Linux 2.6.12 or later.
 
    .. versionadded:: 3.4
 
@@ -206,7 +206,7 @@
    The time limit (in microseconds) on CPU time that a process can spend
    under real-time scheduling without making a blocking syscall.
 
-   Availability: Linux 2.6.25 or later.
+   .. availability:: Linux 2.6.25 or later.
 
    .. versionadded:: 3.4
 
@@ -215,7 +215,7 @@
 
    The number of signals which the process may queue.
 
-   Availability: Linux 2.6.8 or later.
+   .. availability:: Linux 2.6.8 or later.
 
    .. versionadded:: 3.4
 
@@ -225,7 +225,7 @@
    This limits the amount of network memory, and hence the amount of mbufs,
    that this user may hold at any time.
 
-   Availability: FreeBSD 9 or later.
+   .. availability:: FreeBSD 9 or later.
 
    .. versionadded:: 3.4
 
@@ -236,7 +236,7 @@
    This limit is enforced only if bit 1 of the vm.overcommit sysctl is set.
    Please see :manpage:`tuning(7)` for a complete description of this sysctl.
 
-   Availability: FreeBSD 9 or later.
+   .. availability:: FreeBSD 9 or later.
 
    .. versionadded:: 3.4
 
@@ -244,7 +244,7 @@
 
    The maximum number of pseudo-terminals created by this user id.
 
-   Availability: FreeBSD 9 or later.
+   .. availability:: FreeBSD 9 or later.
 
    .. versionadded:: 3.4