Work around GOOGLE_* changes in protobuf >= 22.0

According to the protobuf migration guide as of June 2023 [0], protobuf
22.0 (aka 4.22.0) took a dependency on something called "abseil" and as
a result the "stubs" have been removed. This apparently caused all the
uses of GOOGLE_* identifiers in protoc-c to fail when building against
newer versions of protobuf.

This commit introduces compatibility definitions when building against
protobuf >= 4.22.0 so that protobuf-c can build against older and newer
versions of protobuf.

[0] https://web.archive.org/web/20230611151200/https://protobuf.dev/support/migration/#abseil

protoc-c/c_helpers.h

@@ -178,6 +178,16 @@ inline int FieldSyntax(const FieldDescriptor* field) {
 #endif
 }
 
+// Work around changes in protobuf >= 22.x without breaking compilation against
+// older protobuf versions.
+#if GOOGLE_PROTOBUF_VERSION >= 4022000
+# define GOOGLE_ARRAYSIZE	ABSL_ARRAYSIZE
+# define GOOGLE_CHECK_EQ	ABSL_CHECK_EQ
+# define GOOGLE_CHECK_EQ	ABSL_CHECK_EQ
+# define GOOGLE_DCHECK_GE	ABSL_DCHECK_GE
+# define GOOGLE_LOG		ABSL_LOG
+#endif
+
 }  // namespace c
 }  // namespace compiler
 }  // namespace protobuf