ENH: add exe stuff for cygwin

Modules/Platform/CYGWIN-g77.cmake

@@ -2,4 +2,5 @@ SET(CMAKE_SHARED_LIBRARY_PREFIX "lib")
 SET(CMAKE_SHARED_LIBRARY_SUFFIX ".dll")
 SET(CMAKE_SHARED_LIBRARY_Fortran_FLAGS "") 
 SET(CMAKE_SHARED_LIBRARY_Fortran_FLAGS "")
+SET(CMAKE_EXECUTABLE_SUFFIX ".exe")          # .exe
 INCLUDE(Platform/g77)

Modules/Platform/CYGWIN.cmake

@@ -5,3 +5,4 @@ SET(CMAKE_SHARED_LIBRARY_SUFFIX ".dll")
 # no pic for gcc on cygwin
 SET(CMAKE_SHARED_LIBRARY_C_FLAGS "")
 SET(CMAKE_SHARED_LIBRARY_CXX_FLAGS "")
+SET(CMAKE_EXECUTABLE_SUFFIX ".exe")          # .exe