use a test for PDF support that is more portable across teTeX major versions

(closes SF bug #1238210)

Doc/texinputs/howto.cls

@@ -50,7 +50,8 @@
 %
 \renewcommand{\maketitle}{
   \py@doHorizontalRule
-  \@ifundefined{pdfinfo}{}{{
+  \ifpdf
+    \begingroup
     % This \def is required to deal with multi-line authors; it
     % changes \\ to ', ' (comma-space), making it pass muster for
     % generating document info in the PDF file.
@@ -59,7 +60,8 @@
       /Author (\@author)
       /Title (\@title)
     }
-  }}
+    \endgroup
+  \fi
   \begin{flushright}
     {\rm\Huge\py@HeaderFamily \@title} \par
     {\em\large\py@HeaderFamily \py@release\releaseinfo} \par

Doc/texinputs/manual.cls

@@ -64,7 +64,8 @@
     \let\footnotesize\small
     \let\footnoterule\relax
     \py@doHorizontalRule%
-    \@ifundefined{pdfinfo}{}{{
+    \ifpdf
+      \begingroup
       % This \def is required to deal with multi-line authors; it
       % changes \\ to ', ' (comma-space), making it pass muster for
       % generating document info in the PDF file.
@@ -73,7 +74,8 @@
         /Author (\@author)
         /Title (\@title)
       }
-    }}
+      \endgroup
+    \fi
     \begin{flushright}%
       {\rm\Huge\py@HeaderFamily \@title \par}%
       {\em\LARGE\py@HeaderFamily \py@release\releaseinfo \par}