Add the (deliberately undocumented) sqlite_log() SQL function as a built-in.

FossilOrigin-Name: f7806e03995b314771aa72a08ce55d56d60096cf
diff --git a/src/func.c b/src/func.c
index 6a4f7c0..e75fa47 100644
--- a/src/func.c
+++ b/src/func.c
@@ -775,6 +775,21 @@
 }
 
 /*
+** Implementation of the sqlite_log() function.  This is a wrapper around
+** sqlite3_log().  The return value is NULL.  The function exists purely for
+** its side-effects.
+*/
+static void logFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  UNUSED_PARAMETER(argc);
+  UNUSED_PARAMETER(context);
+  sqlite3_log(sqlite3_value_int(argv[0]), "%s", sqlite3_value_text(argv[1]));
+}
+
+/*
 ** Implementation of the sqlite_compileoption_used() function.
 ** The result is an integer that identifies if the compiler option
 ** was used to build SQLite.
@@ -1541,6 +1556,7 @@
     FUNCTION(nullif,             2, 0, 1, nullifFunc       ),
     FUNCTION(sqlite_version,     0, 0, 0, versionFunc      ),
     FUNCTION(sqlite_source_id,   0, 0, 0, sourceidFunc     ),
+    FUNCTION(sqlite_log,         2, 0, 0, logFunc          ),
 #ifndef SQLITE_OMIT_COMPILEOPTION_DIAGS
     FUNCTION(sqlite_compileoption_used,1, 0, 0, compileoptionusedFunc  ),
     FUNCTION(sqlite_compileoption_get, 1, 0, 0, compileoptiongetFunc  ),