Fix issue #1104 Solaris compilation errors fread()/fwrite()

Explicit std name space for fread() and fwrite().

include/rapidjson/filereadstream.h

@@ -68,7 +68,7 @@ private:
             ++current_;
         else if (!eof_) {
             count_ += readCount_;
-            readCount_ = fread(buffer_, 1, bufferSize_, fp_);
+            readCount_ = std::fread(buffer_, 1, bufferSize_, fp_);
             bufferLast_ = buffer_ + readCount_ - 1;
             current_ = buffer_;
 

include/rapidjson/filewritestream.h

@@ -62,7 +62,7 @@ public:
 
     void Flush() {
         if (current_ != buffer_) {
-            size_t result = fwrite(buffer_, 1, static_cast<size_t>(current_ - buffer_), fp_);
+            size_t result = std::fwrite(buffer_, 1, static_cast<size_t>(current_ - buffer_), fp_);
             if (result < static_cast<size_t>(current_ - buffer_)) {
                 // failure deliberately ignored at this time
                 // added to avoid warn_unused_result build errors