Remove old docs, rename docs_new to docs

It would be probably good idea to also remove tools/docgen.py and
asciidoc.mk, but asciidoc.mk is still mentioned under `cloud/doc`, which
may contain some useful info which we'll need at least to review before
removing.

PUBLISHED_FROM=faf454d4c52a2f07ea8ac084cf0bd11a0c9c9b3b

docs/c-api/util.h/mg_skip.md

@@ -0,0 +1,17 @@
+---
+title: "mg_skip()"
+decl_name: "mg_skip"
+symbol_kind: "func"
+signature: |
+  const char *mg_skip(const char *s, const char *end_string,
+                      const char *delimiters, struct mg_str *v);
+---
+
+Fetch substring from input string `s`, `end` into `v`.
+Skips initial delimiter characters. Records first non-delimiter character
+as the beginning of substring `v`. Then scans the rest of the string
+until a delimiter character or end-of-string is found.
+`delimiters` is a 0-terminated string containing delimiter characters.
+Either one of `delimiters` or `end_string` terminates the search.
+Return an `s` pointer, advanced forward where parsing stopped. 
+