Remove old wrapper code and defines for keeping log() and log(3) apart

This is the non-automated portion of bug 7599.

changes/rename_log_7599

@@ -0,0 +1,4 @@
+  o Code simplification and refactoring:
+    - Rename Tor's logging function log() to tor_log(), to avoid conflicts
+      with the natural logarithm function from the system libm.  Resolves
+      ticket 7599.

src/common/torlog.h

@@ -153,7 +153,6 @@ void set_log_time_granularity(int granularity_msec);
 
 void tor_log(int severity, log_domain_mask_t domain, const char *format, ...)
   CHECK_PRINTF(3,4);
-#define log tor_log /* hack it so we don't conflict with tor_log() as much */
 
 #if defined(__GNUC__) || defined(RUNNING_DOXYGEN)
 extern int log_global_min_severity_;

src/common/util.c

@@ -20,7 +20,6 @@
 #define UTIL_PRIVATE
 #include "util.h"
 #include "torlog.h"
-#undef log
 #include "crypto.h"
 #include "torint.h"
 #include "container.h"
@@ -323,13 +322,13 @@ tor_log_mallinfo(int severity)
  * ===== */
 
 /**
- * Returns the natural logarithm of d base 2.  We define this wrapper here so
- * as to make it easier not to conflict with Tor's tor_log() macro.
+ * Returns the natural logarithm of d base 2.  We defined this wrapper here so
+ * to avoid conflicts with old versions of tor_log(), which were named log().
  */
 double
 tor_mathlog(double d)
 {
-  return tor_log(d);
+  return log(d);
 }
 
 /** Return the long integer closest to <b>d</b>. We define this wrapper