fix misleading indentation in miniz, missing header, and missing forward declarations

source/detail/crypto/sha.cpp

@@ -22,6 +22,7 @@
 // @author: see AUTHORS file
 
 #include <array>
+#include <cstring>
 #include <iomanip>
 #include <string>
 #include <sstream>

source/detail/xlsx_producer.hpp

@@ -35,8 +35,11 @@ class serializer;
 
 namespace xlnt {
 
+class border;
 class cell_reference;
 class color;
+class fill;
+class font;
 class path;
 class relationship;
 class workbook;