tree-wide: use coccinelle to patch a lot of code to use mfree()

This replaces this:

        free(p);
        p = NULL;

by this:

        p = mfree(p);

Change generated using coccinelle. Semantic patch is added to the
sources.

src/shared/conf-parser.c

@@ -232,8 +232,7 @@ static int parse_line(const char* unit,
                                            "Unknown section '%s'. Ignoring.", n);
 
                         free(n);
-                        free(*section);
-                        *section = NULL;
+                        *section = mfree(*section);
                         *section_line = 0;
                         *section_ignored = true;
                 } else {