[OpenMP] Clean-up Fortran tests

* Use "do" for DO loops, there is no "for" in Fortran and it is always
   integer

 * Add -cpp to not rely on file name case

 * Add "implicit none" safety

openmp/runtime/test/transform/tile/do.F90

@@ -2,14 +2,14 @@
 ! It is done 3 times corresponding to every possible fraction of the last
 ! iteration before passing beyond UB.
 
-! RUN: %flang %flags %openmp_flags -fopenmp-version=51 -DUB=16 %s -o %t-ub16.exe
-! RUN: %flang %flags %openmp_flags -fopenmp-version=51 -DUB=17 %s -o %t-ub17.exe
-! RUN: %flang %flags %openmp_flags -fopenmp-version=51 -DUB=18 %s -o %t-ub18.exe
+! RUN: %flang %flags %openmp_flags -fopenmp-version=51 -cpp -DUB=16 %s -o %t-ub16.exe
+! RUN: %flang %flags %openmp_flags -fopenmp-version=51 -cpp -DUB=17 %s -o %t-ub17.exe
+! RUN: %flang %flags %openmp_flags -fopenmp-version=51 -cpp -DUB=18 %s -o %t-ub18.exe
 ! RUN: %t-ub16.exe | FileCheck %s --match-full-lines
 ! RUN: %t-ub17.exe | FileCheck %s --match-full-lines
 ! RUN: %t-ub18.exe | FileCheck %s --match-full-lines
 
-program tile_intfor_1d
+program tile_do_1d
   implicit none
   integer i
   print *, 'do'

openmp/runtime/test/transform/tile/do_2d.f90

@@ -4,7 +4,8 @@
 ! RUN: %t.exe | FileCheck %s --match-full-lines
 
 
-program tile_intfor_2d
+program tile_do_2d
+  implicit none
   integer i, j
   print *, 'do'
 

openmp/runtime/test/transform/tile/do_2d_varsizes.f90

@@ -3,7 +3,8 @@
 ! RUN: %flang %flags %openmp_flags -fopenmp-version=51 %s -o %t.exe
 ! RUN: %t.exe | FileCheck %s --match-full-lines
 
-program tile_intfor_varsizes
+program tile_do_2d_varsizes
+  implicit none
   integer i
 
   call kernel(7,17,3,2)

openmp/runtime/test/transform/unroll/heuristic_do.f90

@@ -4,7 +4,8 @@
 ! RUN: %t.exe | FileCheck %s --match-full-lines
 
 
-program unroll_heuristic
+program unroll_heuristic_do
+  implicit none
   integer :: i
   print *, 'do'