fix(review): address PR #130 review

- proftest: declare the _mkdir_recursive loop index inside the for.
- xmpp/presence: shorten the resource-snapshot comment to one line.
- command/cmd_funcs: report the /vcard remove index error via cons_show_error.
- common: replace g_assert in g_diff_to_gsize with a log_error + return 0
  (moved out of the header into common.c); take get_random_string length as
  size_t instead of asserting non-negative.
- otr: drop the change-narrating comment on the whitespace memmove.

Refs #112

src/common.h

@@ -158,14 +158,7 @@ gboolean create_dir(const char* name);
 gboolean copy_file(const char* const src, const char* const target, const gboolean overwrite_existing);
 char* str_replace(const char* string, const char* substr, const char* replacement);
 gboolean strtoi_range(const char* str, int* saveptr, int min, int max, char** err_msg);
-
-// Pointer-diff to gsize for callers that know end >= start by construction.
-static inline gsize
-g_diff_to_gsize(const void* end, const void* start)
-{
-    g_assert(end >= start);
-    return (gsize)((const char*)end - (const char*)start);
-}
+gsize g_diff_to_gsize(const void* end, const void* start);
 int utf8_display_len(const char* const str);
 gchar* str_xml_sanitize(const char* const str);
 
@@ -186,7 +179,7 @@ int is_regular_file(const char* path);
 int is_dir(const char* path);
 void get_file_paths_recursive(const char* directory, GSList** contents);
 
-gchar* get_random_string(int length);
+gchar* get_random_string(size_t length);
 
 gboolean call_external(gchar** argv);
 gchar** format_call_external_argv(const char* template_fmt, const char* url, const char* filename);