Fortran: Use explicit type in Fortran 90 check

In CMakeTestFortranCompiler we build a test program using a Fortran 90
construct to check whether the compiler supports the language.  Some
compilers have options to require explicit variable types.  Fix the test
program to use an explicit variable type so it passes under such a
configuration.

Suggested-by: Neil Carlson <[email protected]>

Modules/CMakeTestFortranCompiler.cmake

@@ -72,7 +72,7 @@ else()
     message(STATUS "Checking whether ${CMAKE_Fortran_COMPILER} supports Fortran 90")
     file(WRITE ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/testFortranCompilerF90.f90 "
       PROGRAM TESTFortran90
-      stop = 1 ; do while ( stop .eq. 0 ) ; end do
+      integer stop ; stop = 1 ; do while ( stop .eq. 0 ) ; end do
       END PROGRAM TESTFortran90
 ")
     try_compile(CMAKE_Fortran_COMPILER_SUPPORTS_F90 ${CMAKE_BINARY_DIR}