Docs are generated for Mongoose

Comments in headers are changed a bit: removed adoc-specific stuff,
markdown is used instead

PUBLISHED_FROM=9242cce85cc52a47a197d377e7e23804721a6bb5

docs/c-api/mbuf.h/mbuf_insert.md

@@ -0,0 +1,14 @@
+---
+title: "mbuf_insert()"
+decl_name: "mbuf_insert"
+symbol_kind: "func"
+signature: |
+  size_t mbuf_insert(struct mbuf *, size_t, const void *, size_t);
+---
+
+Insert data at a specified offset in the Mbuf.
+
+Existing data will be shifted forwards and the buffer will
+be grown if necessary.
+Return the number of bytes inserted. 
+