Feature freeze for C23

The dust is now settling and we finally should have all proposals for new C23 features. Below you find links to some of the newer ones that I co-authored. Many previous proposals are still open because WG14 only voted in favor and now they have to be revisted before they can be decided.

• Only reserve names of optional functions if necessary. This mitigates the naming explosion in <math.h> and other headers. http://open-std.org/jtc1/sc22/wg14/www/docs/n2839.htm
• Avoid evaluation of sizeof for VLA expressions for which the size is already known http://open-std.org/jtc1/sc22/wg14/www/docs/n2838.htm
• Make call_once mandatory http://open-std.org/jtc1/sc22/wg14/www/docs/n2840.htm
• Identifier Syntax using Unicode Standard Annex 31 http://open-std.org/jtc1/sc22/wg14/www/docs/n2836.pdf
• Unsequenced functions v3. This adds function attributes for possible optimizations http://open-std.org/jtc1/sc22/wg14/www/docs/n2825.htm
• Pointers and integer types. In particular requires types [u]intptr_t http://open-std.org/jtc1/sc22/wg14/www/docs/n2822.htm
• Require exact-width integer type interfaces http://open-std.org/jtc1/sc22/wg14/www/docs/n2821.htm
• Function Pointer Types for Pairing Code and Data. This is indendent of the lambda proposals but should be quite usefull for them http://open-std.org/jtc1/sc22/wg14/www/docs/n2787.pdf