[flang] Rename to Fortran.h, update style guide, run clang-format

Original-commit: flang-compiler/f18@aa2907d2260c34085360917e7fab43d8ee79b6e4
Reviewed-on: https://github.com/flang-compiler/f18/pull/308
Tree-same-pre-rewrite: false
diff --git a/flang/lib/evaluate/intrinsics.cc b/flang/lib/evaluate/intrinsics.cc
index 7d7351e..14de420 100644
--- a/flang/lib/evaluate/intrinsics.cc
+++ b/flang/lib/evaluate/intrinsics.cc
@@ -17,8 +17,8 @@
 #include "fold.h"
 #include "tools.h"
 #include "type.h"
+#include "../common/Fortran.h"
 #include "../common/enum-set.h"
-#include "../common/fortran.h"
 #include "../common/idioms.h"
 #include <algorithm>
 #include <map>