Document run from shared object

Matches root-project/root#14813.

manual/cling/index.md

@@ -257,6 +257,7 @@ This list is also available by typing `.?` or `.help` in the ROOT prompt.
    .L <filename>[flags]: load the given file with optional flags like
                          + to compile or ++ to force recompile.
                          Type .? TSystem::CompileMacro for a list of all flags.
+                         <filename> can also be a shared library; skip flags.
    .(x|X) <filename>[flags](args) :
                          same as .L <filename>[flags] and runs then a function
                          with signature: ret_type filename(args).

manual/first_steps_with_root/index.md

@@ -159,7 +159,7 @@ Here a selection of commands:
 
 `.!<OS_command>`: Accesses the shell of the operating system. For example `.!ls` or `.!pwd`.
 
-`.x <file_name>`: Executes a ROOT macro.
+`.x <file_name>`: Executes a ROOT macro. file_name can be also a precompiled macro or a regular shared library userlib.so (or .dll) with a function userlib(args).
 
 `.U <file_name>`: Unloads a file.
 

manual/root_macros_and_shared_libraries/index.md

@@ -59,13 +59,18 @@ You can execute a ROOT macro in one of three ways:
    >
    > By adding further space-separated file names to the line above, you can sequentially execute multiple
    > macros in the same ROOT session, as long as they don't share the same name.
+   > You can also replace MacroName.C with MacroName_C.so if you compiled your macro with ACLiC beforehand.
 
 2. Execute a macro at the ROOT prompt:
 
    ```
    root [0] .x MacroName.C
    ```
 
+   > **Note**
+   >
+   > You can also replace MacroName.C with MacroName_C.so if you compiled your macro with ACLiC beforehand.
+
 3. Load a macro from within a ROOT session and then call the function:
 
    ```
@@ -77,6 +82,7 @@ You can execute a ROOT macro in one of three ways:
    >
    > You can load multiple macros in the same ROOT session (one .L statement for each),
    > as long as they don't have the same name.
+   > You can also replace MacroName.C with MacroName_C.so if you compiled your macro with ACLiC beforehand.
 
 It is also possible to pass parameters directly to the macro function:
 ```
@@ -157,6 +163,7 @@ root [0] .L MyScript.C+
 The `+` option compiles the code and generates a shared library `MyScript_C.so` (`MyScript_C.dll` on Windows).
 The `+` command rebuilds the library only if the ROOT macro or any of the files it includes
 are newer than the library. To force a recompilation of the library, use `++`.
+Once compiled, the shared library name can be directly passed in place of `MyScript.C` when calling `.L` or `.x`.
 
 You can also compile, build and run with arguments in a one-liner using: