Update .clang-format and check_header.py to C++17

Author: sweemer

.clang-format

@@ -1,6 +1,6 @@
 ---
 Language:        Cpp
-Standard:        c++14
+Standard:        c++17
 
 
 # The following is close to the style we've been using all these years
@@ -33,7 +33,7 @@ PointerAlignment: Left
 
 SortIncludes: true
 IncludeBlocks: Merge
-IncludeCategories: 
+IncludeCategories:
   - Regex:           '^"'
     Priority:        1
   - Regex:           '^<ql/'

tools/check_header.py

@@ -11,7 +11,7 @@ def check(header):
     source_file = header + ".cpp"
     shutil.copy(header, source_file)
     object_file = header + ".o"
-    command = f"{cxx} -std=c++14 -c -Wno-unknown-pragmas -Wall -Werror -I. {source_file} -o {object_file}"
+    command = f"{cxx} -std=c++17 -c -Wno-unknown-pragmas -Wall -Werror -I. {source_file} -o {object_file}"
     print(command, file=sys.stderr)
     code = os.system(command)
     try: