Add FPDF_FreeDefaultSystemFontInfo API

fpdfsdk/fpdf_sysfontinfo.cpp

Index: fpdfsdk/fpdf_sysfontinfo.cpp
diff --git a/fpdfsdk/fpdf_sysfontinfo.cpp b/fpdfsdk/fpdf_sysfontinfo.cpp
index ef62ae3f8a1a39d8e6a651b6671f59acc129aca2..ac6cf28e0bfc7cf67c84f61efa90102fdefe644b 100644
--- a/fpdfsdk/fpdf_sysfontinfo.cpp
+++ b/fpdfsdk/fpdf_sysfontinfo.cpp
@@ -194,3 +194,8 @@ DLLEXPORT FPDF_SYSFONTINFO* STDCALL FPDF_GetDefaultSystemFontInfo() {
   pFontInfoExt->m_pFontInfo = pFontInfo.release();
   return pFontInfoExt;
 }
+
+DLLEXPORT void FPDF_FreeDefaultSystemFontInfo(
+    FPDF_SYSFONTINFO* pDefaultFontInfo) {
+  delete static_cast<FPDF_SYSFONTINFO_DEFAULT*>(pDefaultFontInfo);
+}