api: move verbatim c code out of gendispatch.lua and into c files

Remove max_fname_len check, which caused false successful lookups,
and was an optimization for a very rare case.

src/nvim/api/private/dispatch.c

@@ -0,0 +1,45 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <assert.h>
+#include <msgpack.h>
+
+#include "nvim/map.h"
+#include "nvim/log.h"
+#include "nvim/vim.h"
+#include "nvim/msgpack_rpc/helpers.h"
+#include "nvim/api/private/dispatch.h"
+#include "nvim/api/private/helpers.h"
+#include "nvim/api/private/defs.h"
+
+#include "nvim/api/buffer.h"
+#include "nvim/api/tabpage.h"
+#include "nvim/api/ui.h"
+#include "nvim/api/vim.h"
+#include "nvim/api/window.h"
+
+static Map(String, MsgpackRpcRequestHandler) *methods = NULL;
+
+static void msgpack_rpc_add_method_handler(String method,
+                                           MsgpackRpcRequestHandler handler)
+{
+  map_put(String, MsgpackRpcRequestHandler)(methods, method, handler);
+}
+
+MsgpackRpcRequestHandler msgpack_rpc_get_handler_for(const char *name,
+                                                     size_t name_len)
+{
+  String m = { .data = (char *)name, .size = name_len };
+  MsgpackRpcRequestHandler rv =
+    map_get(String, MsgpackRpcRequestHandler)(methods, m);
+
+  if (!rv.fn) {
+    rv.fn = msgpack_rpc_handle_missing_method;
+  }
+
+  return rv;
+}
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+#include "api/private/dispatch_wrappers.generated.h"
+#endif