Add additional C++ filename extensions

These are all supported by GCC: https://gcc.gnu.org/onlinedocs/gcc-14.2.0/gcc/Overall-Options.html

mesonbuild/compilers/compilers.py

@@ -53,7 +53,7 @@
 # First suffix is the language's default.
 lang_suffixes: T.Mapping[str, T.Tuple[str, ...]] = {
     'c': ('c',),
-    'cpp': ('cpp', 'cppm', 'cc', 'cxx', 'c++', 'hh', 'hpp', 'ipp', 'hxx', 'ino', 'ixx', 'C', 'H'),
+    'cpp': ('cpp', 'cppm', 'cc', 'cp', 'cxx', 'c++', 'hh', 'hp', 'hpp', 'ipp', 'hxx', 'h++', 'ino', 'ixx', 'CPP', 'C', 'HPP', 'H'),
     'cuda': ('cu',),
     # f90, f95, f03, f08 are for free-form fortran ('f90' recommended)
     # f, for, ftn, fpp are for fixed-form fortran ('f' or 'for' recommended)