Fix page-break-inside:avoid to work for nested tags too

The initial version was too naïve and didn't work correctly if the <div>
with this style had nested elements.

samples/html/printing/test.htm

@@ -55,6 +55,8 @@ is split into base and GUI libraries.
 
 <P>
 
+<!-- Avoid page breaks inside individual version change logs -->
+<div style="page-break-inside:avoid">
 <H2>Release 2.1.11 (final)</H2>
 
 <ul>
@@ -71,18 +73,22 @@ combined base/GUI library for GUI applications only.
 <li>Rewritten timer.cpp, possible wxChrono class.
 <li>Bug tracking system in place.
 </ul>
+</div>
 
 <P>
 
+<div style="page-break-inside:avoid">
 <H4>Release 2.1.12</H4>
 
 <ul>
 <li>Release date: January 9th, 2000
 <li>Miscellaneous fixes and small enhancements.
 </ul>
+</div>
 
 <P>
 
+<div style="page-break-inside:avoid">
 <H4>Release 2.1.13</H4>
 
 <ul>
@@ -90,6 +96,7 @@ combined base/GUI library for GUI applications only.
 <li>Miscellaneous fixes and small enhancements.
 <li>wxDateTime class in beta.
 </ul>
+</div>
 
 <P>
 
@@ -102,6 +109,7 @@ combined base/GUI library for GUI applications only.
 
 <P>
 
+<div style="page-break-inside:avoid">
 <H2>Release 2.2.x (final)</H2>
 
 <ul>
@@ -109,15 +117,18 @@ combined base/GUI library for GUI applications only.
 <li>Unicode compilation working in wxGTK and wxMSW.
 <li>wxDateTime class.
 </ul>
+</div>
 
 <P>
 
+<div style="page-break-inside:avoid">
 <H2>Release 2.3.x (final)</H2>
 
 <ul>
 <li>Release date: unknown
 <li>WinCE port available.
 </ul>
+</div>
 
 <P>