Doxygen comment parsing fix for empty lines in code/verbatim blocks

Fix how end of paragraph is identified when parsing \code and
\verbatim blocks that appear within a paragraph and contain an empty
line.  Previously this would generate a warning for unexpected end of
doxygen comments, and it could generate a segfault due to
dereferencing an invalid iterator value.

The doxygen_basic_translate.i and doxygen_basic_translate_style2.i
tests have been updated to serve as regression tests for this
behavior.  Prior to this fix, inclusion of the empty code block line
in this context produced a segfault.

Examples/test-suite/java/doxygen_basic_translate_runme.java

@@ -54,6 +54,8 @@ public class doxygen_basic_translate_runme {
     		" \n" +
     		" {@code \n" +
     		"int main() { while(true); } \n" +
+		"\n" +
+		"// Test blank line in code block \n" +
     		" }\n" +
     		" }\n" +
     		" \n" +