Add .h++ extension for header files

This fixes #8111 (which I just opened).

Let me know if changes are needed. I have essentially followed what I saw in 77ac48e2d0874d152c29b597113053f2629b3bc3 (which fixes #302 which is a similar issue affecting source files with `.c++` extension).

Closes #8112.

PiperOrigin-RevId: 253532672
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java
index 1ccaf58..4200946 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppFileTypes.java
@@ -41,7 +41,8 @@
       FileTypeSet.of(CppFileTypes.CPP_SOURCE, CppFileTypes.C_SOURCE);
 
   public static final FileType CPP_HEADER =
-      FileType.of(".h", ".hh", ".hpp", ".ipp", ".hxx", ".inc", ".inl", ".tlh", ".tli", ".H");
+      FileType.of(
+          ".h", ".hh", ".hpp", ".ipp", ".hxx", ".h++", ".inc", ".inl", ".tlh", ".tli", ".H");
   public static final FileType PCH = FileType.of(".pch");
   public static final FileTypeSet OBJC_HEADER = FileTypeSet.of(CPP_HEADER, PCH);