auto merge of #20058 : Kimundi/rust/str_pattern_pre, r=alexcrichton

This stabilizes most methods on `&str` working with patterns in a way that is forwards-compatible with a generic string pattern matching API:
- Methods that are using the primary name for their operation are marked as `#[stable]`, as they can be upgraded to a full `Pattern` API later without existing code breaking. Example: `contains(&str)`
- Methods that are using a more specific name in order to not clash with the primary one are marked as `#[unstable]`, as they will likely be removed once their functionality is merged into the primary one. Example: `contains_char<C: CharEq>(C)`
- The method docs got changed to consistently refer to the pattern types as a pattern.
- Methods whose names do not match in the context of the more generic API got renamed. Example: `trim_chars -> trim_matches` 

Additionally, all methods returning iterators got changed to return unique new types with changed names in accordance with the new naming guidelines.

See also https://github.com/rust-lang/rfcs/pull/528

Due to some deprecations and type changes, this is a 

[breaking-change]

src/libstd/path/windows.rs

@@ -26,7 +26,7 @@ use mem;
 use option::Option;
 use option::Option::{Some, None};
 use slice::SliceExt;
-use str::{CharSplits, FromStr, StrVector, StrExt};
+use str::{SplitTerminator, FromStr, StrVector, StrExt};
 use string::{String, ToString};
 use unicode::char::UnicodeChar;
 use vec::Vec;
@@ -38,7 +38,7 @@ use super::{contains_nul, BytesContainer, GenericPath, GenericPathUnsafe};
 /// Each component is yielded as Option<&str> for compatibility with PosixPath, but
 /// every component in WindowsPath is guaranteed to be Some.
 pub type StrComponents<'a> =
-    Map<&'a str, Option<&'a str>, CharSplits<'a, char>, fn(&'a str) -> Option<&'a str>>;
+    Map<&'a str, Option<&'a str>, SplitTerminator<'a, char>, fn(&'a str) -> Option<&'a str>>;
 
 /// Iterator that yields successive components of a Path as &[u8]
 pub type Components<'a> =