exported_symbols: comment old symbols

exported_symbols: comment old symbols

Fix versioning for updated symbols dm_stats_create_region
and dm_stats_create_region.

Only the latest symbol should have global entry.

Since I'm not sure what is currenlty the best option for
old symbols - we added support for easy commenting of them
(so we do not lose information when the symbol appeared
for the first time.)

Note: some old already deleted symbols should have been
restored as comments.