pdf: ocr: small fixes, plus make pdfocr redefinable in subdirs

src/doc/user/recoll.conf.xml

@@ -686,8 +686,8 @@ with possibly meaning-altering missing words.</para></listitem></varlistentry>
 <varlistentry id="RCL.INSTALL.CONFIG.RECOLLCONF.PDFOCR">
 <term><varname>pdfocr</varname></term>
 <listitem><para>Attempt OCR of PDF files with no text content if both tesseract and
-pdftoppm are installed. The default is off because OCR is so
-very slow.</para></listitem></varlistentry>
+pdftoppm are installed. This can be defined in subdirectories. The default is off because
+OCR is so very slow.</para></listitem></varlistentry>
 <varlistentry id="RCL.INSTALL.CONFIG.RECOLLCONF.PDFOCRLANG">
 <term><varname>pdfocrlang</varname></term>
 <listitem><para>Language to assume for PDF OCR. This is very important for having a reasonable rate of errors

src/doc/user/usermanual.html

@@ -9551,7 +9551,8 @@ for i in range(nres):
                 "RCL.INSTALL.CONFIG.RECOLLCONF.PDFOCR"></a><span class="term"><code class="varname">pdfocr</code></span></dt>
                 <dd>
                   <p>Attempt OCR of PDF files with no text content
-                  if both tesseract and pdftoppm are installed. The
+                  if both tesseract and pdftoppm are installed.
+                  This can be defined in subdirectories. The
                   default is off because OCR is so very slow.</p>
                 </dd>
                 <dt><a name=