Fix compilation with -std=c++17

[Feyorsh]

Fixes #36840.

0c96d61: I don't think there should be any issues with this, as it should be exactly what cpdef does under the hood. That being said, I'd like someone knowledgable with Cython to sanity check this.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation accordingly.

⌛ Dependencies

N/A

[mkoeppe]

Other than the whitespace fix, LGTM.

[mkoeppe]

Looking good, thanks.

[mkoeppe]

Build fails for me on macOS (tried as part of #37584)

[sagelib-10.3]     building 'sage.modular.arithgroup.farey_symbol' extension
[sagelib-10.3]     gcc -fno-strict-overflow -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -O3 -Wall -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk -g -O2 -Isage/modular/arithgroup -I/Users/mkoeppe/s/sage/sage-rebasing/worktree-green/local/var/lib/sage/venv-python3.12/lib/python3.12/site-packages/cysignals -Isage/cpython -I/Users/mkoeppe/s/sage/sage-rebasing/worktree-green/src -I/Users/mkoeppe/s/sage/sage-rebasing/worktree-green/local/var/lib/sage/venv-python3.12/lib/python3.12/site-packages/numpy/core/include -I/usr/local/opt/python@3.12/Frameworks/Python.framework/Versions/3.12/include/python3.12 -I/Users/mkoeppe/s/sage/sage-rebasing/worktree-green/local/var/lib/sage/venv-python3.12/include -I/usr/local/opt/python@3.12/Frameworks/Python.framework/Versions/3.12/include/python3.12 -c sage/modular/arithgroup/farey.cpp -o build/temp.macosx-14.0-x86_64-cpython-312/sage/modular/arithgroup/farey.o
[sagelib-10.3]     sage/modular/arithgroup/farey.cpp:455:26: warning: comparison of integers of different signs: 'int' and 'size_type' (aka 'unsigned long') [-Wsign-compare]
[sagelib-10.3]           if( missing_pair+1 == pairing.size() ) {
[sagelib-10.3]               ~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~
[sagelib-10.3]     sage/modular/arithgroup/farey.cpp:497:34: warning: comparison of integers of different signs: 'const int' and 'size_t' (aka 'unsigned long') [-Wsign-compare]
[sagelib-10.3]           if( pairing[j] == NO and i != j ) {
[sagelib-10.3]                                    ~ ^  ~
[sagelib-10.3]     sage/modular/arithgroup/farey.cpp:562:21: warning: comparison of integers of different signs: 'typename __wrap_iter<const int *>::difference_type' (aka 'long') and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]
[sagelib-10.3]         if( i-p.begin() != n ) {
[sagelib-10.3]             ~~~~~~~~~~~ ^  ~
[sagelib-10.3]     sage/modular/arithgroup/farey.cpp:699:17: warning: comparison of integers of different signs: 'int' and 'size_t' (aka 'unsigned long') [-Wsign-compare]
[sagelib-10.3]       for(int i=0; i<number_of_cusps(); i++) {
[sagelib-10.3]                    ~^~~~~~~~~~~~~~~~~~
[sagelib-10.3]     sage/modular/arithgroup/farey.cpp:741:19: error: use of undeclared identifier 'bind'; did you mean 'find'?
[sagelib-10.3]                       bind(greater<int>(), placeholders::_1, 0))/2;
[sagelib-10.3]                       ^~~~
[sagelib-10.3]                       find

[mkoeppe]

This fixes it.

[github-actions]

Documentation preview for this PR (built with commit 39db3c5; changes) is ready! 🎉