Doxygen: rename all .dox files to end with .md

Using a standard ending here will let other tools that expect
markdown understand our output here.

This commit was automatically generated with:

   for fn in $(find src -name '*.dox'); do \
      git mv "$fn" "${fn%.dox}.md"; \
   done

1 files changed, 0 insertions, 6 deletions

diff --git a/src/lib/compress/lib_compress.dox b/src/lib/compress/lib_compress.dox
deleted file mode 100644
index c43f223fe7..0000000000
--- a/src/lib/compress/lib_compress.dox
+++ /dev/null
@@ -1,6 +0,0 @@
-@dir /lib/compress
-@brief lib/compress: Wraps several compression libraries
-
-Currently supported are zlib (mandatory), zstd (optional), and lzma
-(optional).
-