Change suffix to f90

No more preprocessor directive in the file.

Inst_eddies/CMakeLists.txt

 # inst_eddies:
-add_executable(inst_eddies inst_eddies.f90 local_extrema.f90 set_max_speed.F90
+add_executable(inst_eddies inst_eddies.f90 local_extrema.f90 set_max_speed.f90
   get_1_outerm.f90 good_contour.f90 mean_speed.f90 set_contours.f90
   nearby_extr.f90 get_var.f90 config.f90 input_ssh.f90 shpc_create.f90
   write_snapshot.f90 ccw_orient.f90 write_eddy.f90 set_all_extr.f90
@@ -25,7 +25,7 @@ target_sources(test_good_contour PRIVATE good_contour.f90)
 target_sources(test_mean_speed PRIVATE mean_speed.f90)
 target_sources(test_nearby_extr PRIVATE nearby_extr.f90)
 target_sources(test_local_extrema PRIVATE local_extrema.f90)
-target_sources(test_set_max_speed PRIVATE set_max_speed.F90 good_contour.f90
+target_sources(test_set_max_speed PRIVATE set_max_speed.f90 good_contour.f90
   mean_speed.f90 get_var.f90 config.f90 input_ssh.f90 shpc_create.f90
   ccw_orient.f90 write_eddy.f90 complete_ssh.f90)
 target_sources(test_write_null PRIVATE shpc_create.f90)
@@ -33,4 +33,4 @@ target_sources(test_complete_ssh PRIVATE complete_ssh.f90)
 target_sources(examine_eddy PRIVATE config.f90 input_ssh.f90 get_var.f90
   shpc_create.f90 set_all_extr.f90 local_extrema.f90 write_eddy.f90
   set_contours.f90 get_1_outerm.f90 ccw_orient.f90 good_contour.f90
-  set_max_speed.F90 complete_ssh.f90 mean_speed.f90)
+  set_max_speed.f90 complete_ssh.f90 mean_speed.f90)