libsepol/secilc/docs: Update the CIL documentation

Update the CIL documentation for the in-statement processing and
duplicate macro and block declarations with block inheritance.

Duplicate macro and block declarations are allowed if they occur as
the result of block inheritance. Document the fact that inherited
macros are overridden by any macros already declared in a
namespace and that declaring a block in a namespace that will
inherit a block with the same name can be used to allow in-statements
to be used on the block.

The new in-statement syntax still supports the old syntax but adds
the ability to specify whether the in-statement should be resolved
before or after block inheritance is resolved.

Signed-off-by: James Carter <jwcart2@gmail.com>

secilc/docs/cil_call_macro_statements.md

@@ -60,6 +60,8 @@ Declare a macro in the current namespace with its associated parameters. The mac
 
 [`tunable`](cil_conditional_statements.md#tunable), [`in`](cil_container_statements.md#in), [`block`](cil_container_statements.md#block), [`blockinherit`](cil_container_statements.md#blockinherit), [`blockabstract`](cil_container_statements.md#blockabstract), and other [`macro`](cil_call_macro_statements.md#macro) statements are not allowed in [`macro`](cil_call_macro_statements.md#macro) blocks.
 
+Duplicate [`macro`](cil_call_macro_statements.md#macro) declarations in the same namespace will normally cause an error, but inheriting a macro into a namespace (with [`blockinherit`](cil_container_statements.md#blockinherit)) that already has a macro with the same name will only result in a warning message and not cause an error. This behavior allows inherited macros to be overridden with local ones.
+
 **Statement definition:**
 
 ```secil

secilc/docs/cil_container_statements.md

@@ -10,6 +10,8 @@ Not allowed in [`macro`](cil_call_macro_statements.md#macro) and [`optional`](ci
 
 [`sensitivity`](cil_mls_labeling_statements.md#sensitivity) and [`category`](cil_mls_labeling_statements.md#category) statements are not allowed in [`block`](cil_container_statements.md#block) blocks.
 
+Duplicate declarations of a [`block`](cil_container_statements.md#block) in the same namespace will normally cause an error, but inheriting a block into a namespace (with [`blockinherit`](cil_container_statements.md#blockinherit)) that already has a block with the same name will only result in a warning message and not cause an error. The policy from both blocks will end up in the binary policy. This behavior was used in the past to allow a block to be declared so that an [`in-statement`](cil_container_statements.md#in) could be used on it, but now an [`in-statement`](cil_container_statements.md#in) can be specified to occur after inheritance, so this behavior is not necessary (but is still allowed).
+
 **Statement definition:**
 
 ```secil
@@ -278,7 +280,7 @@ This example will instantiate the optional block `ext_gateway.move_file` into po
 in
 --
 
-Allows the insertion of CIL statements into a named container ([`block`](cil_container_statements.md#block), [`optional`](cil_container_statements.md#optional) or [`macro`](cil_call_macro_statements.md#macro)).
+Allows the insertion of CIL statements into a named container ([`block`](cil_container_statements.md#block), [`optional`](cil_container_statements.md#optional) or [`macro`](cil_call_macro_statements.md#macro)). This insertion can be specified to occur either before or after block inheritance has been resolved.
 
 Not allowed in [`macro`](cil_call_macro_statements.md#macro), [`booleanif`](cil_conditional_statements.md#booleanif), and other [`in`](cil_container_statements.md#in) blocks.
 
@@ -287,7 +289,7 @@ Not allowed in [`macro`](cil_call_macro_statements.md#macro), [`booleanif`](cil_
 **Statement definition:**
 
 ```secil
-    (in container_id
+    (in [before|after] container_id
         cil_statement
         ...
     )
@@ -306,10 +308,14 @@ Not allowed in [`macro`](cil_call_macro_statements.md#macro), [`booleanif`](cil_
 <td align="left"><p>The <code>in</code> keyword.</p></td>
 </tr>
 <tr class="even">
+<td align="left"><p><code>before|after</code></p></td>
+<td align="left"><p>An optional value that specifies whether to process the [`in`](cil_container_statements.md#in) <code>before</code> or <code>after</code> block inheritance. If no value is specified, then the [`in`](cil_container_statements.md#in) will be processed before block inheritance.</p></td>
+</tr>
+<tr class="odd">
 <td align="left"><p><code>container_id</code></p></td>
 <td align="left"><p>A valid <code>block</code>, <code>optional</code> or <code>macro</code> namespace identifier.</p></td>
 </tr>
-<tr class="odd">
+<tr class="even">
 <td align="left"><p><code>cil_statement</code></p></td>
 <td align="left"><p>Zero or more valid CIL statements.</p></td>
 </tr>