v2.7.1 - bugfix release

• Bugfixes
  • msvc build fixes (Alexander Usyskin)
  • cleanup passwords after use (Alexander Usyskin)
  • drop RANDFILE in owsmangencert.h (kkaempf)
  • fix potential NULL pointer dereference (Alexander Usyskin)
  • MinGW build enablement (Bastian Germann)