Message 186248 - Python tracker

Here is an updated patch. Some comments added (I will be grateful for help in the improvement of these comments), an implementation moved to stringlib (a new file Objects/stringlib/replace.h added).

unicode_2.patch optimizes only too special case and I consider this is not worth the effort. str_replace_1char*.patch cover a wider area and designed to be faster than 3.2 and 3.3 in most cases and not to be significant slower in corner cases.