clean/extend some module docs, including fix from #18403

src/common/backtrace.c

@@ -6,6 +6,11 @@
  *
  * \brief Functions to produce backtraces on bugs, crashes, or assertion
  * failures.
+ *
+ * Currently, we've only got an implementation here using the backtrace()
+ * family of functions, which are sometimes provided by libc and sometimes
+ * provided by libexecinfo.  We tie into the sigaction() backend in order to
+ * detect crashes.
  */
 
 #define __USE_GNU

src/common/compat.c

@@ -6,7 +6,7 @@
 /**
  * \file compat.c
  * \brief Wrappers to make calls more portable.  This code defines
- * functions such as tor_malloc, tor_snprintf, get/set various data types,
+ * functions such as tor_snprintf, get/set various data types,
  * renaming, setting socket options, switching user IDs.  It is basically
  * where the non-portable items are conditionally included depending on
  * the platform.

src/common/crypto.c

@@ -7,7 +7,8 @@
 /**
  * \file crypto.c
  * \brief Wrapper functions to present a consistent interface to
- * public-key and symmetric cryptography operations from OpenSSL.
+ * public-key and symmetric cryptography operations from OpenSSL and
+ * other places.
  **/
 
 #include "orconfig.h"