Fixed several typos

src/doc/guide-strings.md

@@ -155,7 +155,7 @@ println!("{}", s[0]);
 This does not compile. This is on purpose. In the world of UTF-8, direct
 indexing is basically never what you want to do. The reason is that each
 character can be a variable number of bytes. This means that you have to iterate
-through the characters anyway, which is a O(n) operation. 
+through the characters anyway, which is an O(n) operation.
 
 There's 3 basic levels of unicode (and its encodings):
 

src/doc/reference.md

@@ -2526,7 +2526,7 @@ The currently implemented features of the reference compiler are:
 
 * `plugin_registrar` - Indicates that a crate has [compiler plugins][plugin] that it
                        wants to load. As with `phase`, the implementation is
-                       in need of a overhaul, and it is not clear that plugins
+                       in need of an overhaul, and it is not clear that plugins
                        defined using this will continue to work.
 
 * `quote` - Allows use of the `quote_*!` family of macros, which are
@@ -2583,7 +2583,7 @@ there isn't a parser error first). The directive in this case is no longer
 necessary, and it's likely that existing code will break if the feature isn't
 removed.
 
-If a unknown feature is found in a directive, it results in a compiler error.
+If an unknown feature is found in a directive, it results in a compiler error.
 An unknown feature is one which has never been recognized by the compiler.
 
 # Statements and expressions
@@ -2685,7 +2685,7 @@ When an lvalue is evaluated in an _lvalue context_, it denotes a memory
 location; when evaluated in an _rvalue context_, it denotes the value held _in_
 that memory location.
 
-When an rvalue is used in lvalue context, a temporary un-named lvalue is
+When an rvalue is used in an lvalue context, a temporary un-named lvalue is
 created and used instead. A temporary's lifetime equals the largest lifetime
 of any reference that points to it.
 
@@ -2833,7 +2833,7 @@ foo().x;
 ```
 
 A field access is an [lvalue](#lvalues,-rvalues-and-temporaries) referring to
-the value of that field. When the type providing the field inherits mutabilty,
+the value of that field. When the type providing the field inherits mutability,
 it can be [assigned](#assignment-expressions) to.
 
 Also, if the type of the expression to the left of the dot is a pointer, it is
@@ -3321,7 +3321,7 @@ between `_` and `..` is that the pattern `C(_)` is only type-correct if `C` has
 exactly one argument, while the pattern `C(..)` is type-correct for any enum
 variant `C`, regardless of how many arguments `C` has.
 
-Used inside a array pattern, `..` stands for any number of elements, when the
+Used inside an array pattern, `..` stands for any number of elements, when the
 `advanced_slice_patterns` feature gate is turned on. This wildcard can be used
 at most once for a given array, which implies that it cannot be used to
 specifically match elements that are at an unknown distance from both ends of a
@@ -3584,7 +3584,7 @@ is not a surrogate), represented as a 32-bit unsigned word in the 0x0000 to
 0xD7FF or 0xE000 to 0x10FFFF range. A `[char]` array is effectively an UCS-4 /
 UTF-32 string.
 
-A value of type `str` is a Unicode string, represented as a array of 8-bit
+A value of type `str` is a Unicode string, represented as an array of 8-bit
 unsigned bytes holding a sequence of UTF-8 codepoints. Since `str` is of
 unknown size, it is not a _first class_ type, but can only be instantiated
 through a pointer type, such as `&str` or `String`.