doxygen: unify use of \file across the board

Considering the various styles and implications found in the sources, edit
scores of files to follow the same API doc guidelines around the doxygen
grouping and the \file tag.

Many files now show a short description in the generated API doc that was so
far only available as C comment.

The guidelines and reasoning behind it is documented at
https://osmocom.org/projects/cellular-infrastructure/wiki/Guidelines_for_API_documentation

In some instances, remove file comments and add to the corresponding group
instead, to be shared among several files (e.g. bitvec).

Change-Id: Ifa70e77e90462b5eb2b0457c70fd25275910c72b
diff --git a/src/gsm/comp128v23.c b/src/gsm/comp128v23.c
index 1797ebc..12f8a4c 100644
--- a/src/gsm/comp128v23.c
+++ b/src/gsm/comp128v23.c
@@ -1,11 +1,11 @@
-/* COMP128 version 2 and 3 implementation
+/*! \file comp128v23.c
+ * COMP128 version 2 and 3 implementation, common algorithm used for GSM Authentication (A3/A8).
  *
  * This code is a C conversion of the original code from
  * http://www.hackingprojects.net/
- *
  */
-
-/* (C) 2013 by Kévin Redon <kevredon@mail.tsaitgaist.info>
+/*
+ * (C) 2013 by Kévin Redon <kevredon@mail.tsaitgaist.info>
  *
  * All Rights Reserved
  *
@@ -30,11 +30,7 @@
 
 /*! \addtogroup auth
  *  @{
- */
-
-/*! \file comp128v23.c
- *  COMP128 v2 / v3; Common Algorithm used for GSM Authentication (A3/A8)
- */
+ * \file comp128v23.c */
 
 static const uint8_t table0[256] = {
 	197, 235, 60, 151, 98, 96, 3, 100, 248, 118, 42, 117, 172, 211, 181, 203, 61,