Doc: corrected snippet issue in Defining Plugins doc

Task-number: QTBUG-44629
Change-Id: I70e20209b6b33f7adcbcafc6b7d959660cdc2e87
Reviewed-by: Martin Smith <martin.smith@digia.com>

src/corelib/doc/qtcore.qdocconf

@@ -36,7 +36,8 @@ exampledirs += \
                ../ \
                snippets \
                ../../../examples/corelib \
-               ../../../examples/network/dnslookup
+               ../../../examples/network/dnslookup \
+               ../../../examples/widgets/tools
 
 imagedirs   += images
 

src/corelib/plugin/qplugin.qdoc

@@ -44,7 +44,7 @@
     to the interface class called \a ClassName. The \a Identifier must
     be unique. For example:
 
-    \snippet code/doc_src_qplugin.cpp 0
+    \snippet plugandpaint/interfaces.h 3
 
     This macro is normally used right after the class definition for
     \a ClassName, in a header file. See the