Document that Match calls FcFontRenderPrepare (bug 13162).

The behaviour of FcFontMatch and FcFontSetMatch is hard to understand without
knowing that they call FcFontRenderPrepare.

doc/fcconfig.fncs

@@ -243,9 +243,13 @@ if the substitution cannot be performed (due to allocation failure). Otherwise r
 @TYPE3@		FcResult *                      @ARG3@          result
 @PURPOSE@	Return best font
 @DESC@
-Returns the font in <parameter>config</parameter> most close matching <parameter>p</parameter>.  This function
-should be called only after FcConfigSubstitute and FcDefaultSubstitute have
-been called for <parameter>p</parameter>; otherwise the results will not be correct.
+Finds the font in <parameter>sets</parameter> most closely matching
+<parameter>pattern</parameter> and returns the result of
+<function>FcFontRenderPrepare</function> for that font and the provided
+pattern. This function should be called only after
+<function>FcConfigSubstitute</function> and
+<function>FcDefaultSubstitute</function> have been called for
+<parameter>p</parameter>; otherwise the results will not be correct.
 @@
 
 @RET@           FcFontSet *
@@ -267,7 +271,7 @@ been called for <parameter>p</parameter>; otherwise the results will not be corr
 The returned FcFontSet references FcPattern structures which may be shared
 by the return value from multiple FcFontSort calls, applications must not
 modify these patterns.  Instead, they should be passed, along with <parameter>p</parameter> to
-FcFontRenderPrepare which combines them into a complete pattern.
+<function>FcFontRenderPrepare</function> which combines them into a complete pattern.
     </para><para>
 The FcFontSet returned by FcFontSort is destroyed by caling FcFontSetDestroy.
 @@

doc/fcfontset.fncs

@@ -73,10 +73,14 @@ the set of unique such patterns.
 @TYPE5@		FcResult *			@ARG5@		result
 @PURPOSE@	Return the best font from a set of font sets
 @DESC@
-Returns the font in <parameter>sets</parameter> most close matching
-<parameter>pattern</parameter>.  This function should be called only after
-FcConfigSubstitute and FcDefaultSubstitute have been called for
+Finds the font in <parameter>sets</parameter> most closely matching
+<parameter>pattern</parameter> and returns the result of
+<function>FcFontRenderPrepare</function> for that font and the provided
+pattern. This function should be called only after
+<function>FcConfigSubstitute</function> and
+<function>FcDefaultSubstitute</function> have been called for
 <parameter>pattern</parameter>; otherwise the results will not be correct.
+Returns NULL if an error occurs during this process.
 @@
 
 @RET@		void
@@ -116,7 +120,7 @@ The returned FcFontSet references FcPattern structures which may be shared
 by the return value from multiple FcFontSort calls, applications cannot
 modify these patterns.  Instead, they should be passed, along with
 <parameter>pattern</parameter> to
-FcFontRenderPrepare which combines them into a complete pattern.
+<function>FcFontRenderPrepare</function> which combines them into a complete pattern.
     </para><para>
 The FcFontSet returned by FcFontSetSort is destroyed by caling FcFontSetDestroy.
 @@