libstdc++-6.dll and libgcc_s_seh-1.dll are runtime libraries from GCC, the GNU 
Compiler Collection.
These libraries are included here without the corresponding source, as allowed 
by the GCC Runtime Exception: 
https://gcc.gnu.org/onlinedocs/libstdc++/manual/license.html .
The corresponding source can be found at https://gcc.gnu.org/ .
