gh-107298: Fix more Sphinx warnings in the C API doc (#107329)

Declare the following functions as macros, since they are actually
macros. It avoids a warning on "TYPE" or "macro" argument.

* PyMem_New()
* PyMem_Resize()
* PyModule_AddIntMacro()
* PyModule_AddStringMacro()
* PyObject_GC_New()
* PyObject_GC_NewVar()
* PyObject_New()
* PyObject_NewVar()

Add C standard C types to nitpick_ignore in Doc/conf.py:

* int64_t
* uint64_t
* uintptr_t

No longer ignore non existing "__int" type in nitpick_ignore.

Update Doc/tools/.nitignore