cmFortranParser: Inject a newline at end-of-file when missing

Our parser grammar expects all statements to end in an `EOSTMT` token
such as a newline.  Ensure that the last statement in a file can be
parsed even if it is missing a newline.

Source/cmFortranParser.h

@@ -118,11 +118,13 @@ struct cmFortranFile
     : File(file)
     , Buffer(buffer)
     , Directory(dir)
+    , LastCharWasNewline(false)
   {
   }
   FILE* File;
   YY_BUFFER_STATE Buffer;
   std::string Directory;
+  bool LastCharWasNewline;
 };
 
 struct cmFortranParser_s

Source/cmFortranParserImpl.cxx

@@ -119,8 +119,19 @@ int cmFortranParser_Input(cmFortranParser* parser, char* buffer,
   // Read from the file on top of the stack.  If the stack is empty,
   // the end of the translation unit has been reached.
   if (!parser->FileStack.empty()) {
-    FILE* file = parser->FileStack.top().File;
-    return (int)fread(buffer, 1, bufferSize, file);
+    cmFortranFile& ff = parser->FileStack.top();
+    FILE* file = ff.File;
+    size_t n = fread(buffer, 1, bufferSize, file);
+    if (n > 0) {
+      ff.LastCharWasNewline = buffer[n - 1] == '\n';
+    } else if (!ff.LastCharWasNewline) {
+      // The file ended without a newline.  Inject one so
+      // that the file always ends in an end-of-statement.
+      buffer[0] = '\n';
+      n = 1;
+      ff.LastCharWasNewline = true;
+    }
+    return (int)n;
   }
   return 0;
 }