doc/examples: update README.

doc/examples/README

@@ -5,14 +5,19 @@ Both following use cases rely on pkg-config and make, thus make sure
 that you have them installed and working on your system.
 
 
-1) Build the installed examples in a generic read/write user directory
+Method 1: build the installed examples in a generic read/write user directory
 
 Copy to a read/write user directory and just use "make", it will link
 to the libraries on your system, assuming the PKG_CONFIG_PATH is
 correctly configured.
 
-2) Build the examples in-tree
+Method 2: build the examples in-tree
 
 Assuming you are in the source FFmpeg checkout directory, you need to build
-FFmpeg (no need to make install in any prefix). Then you can go into
-doc/examples and run a command such as PKG_CONFIG_PATH=pc-uninstalled make.
+FFmpeg (no need to make install in any prefix). Then just run "make examples".
+This will build the examples using the FFmpeg build system. You can clean those
+examples using "make examplesclean"
+
+If you want to try the dedicated Makefile examples (to emulate a the first
+method), go into doc/examples and run a command such as
+PKG_CONFIG_PATH=pc-uninstalled make.