Change block/statement/expression body not to be definitions

This is half of what dotnet#999 was trying to do; the rest requires some
more work.

Author: jskeet

standard/classes.md

@@ -2021,13 +2021,13 @@ The optional *formal_parameter_list* specifies the parameters of the method ([§
 
 The *return_type* or *ref_return_type*, and each of the types referenced in the *formal_parameter_list* of a method, shall be at least as accessible as the method itself ([§7.5.5](basic-concepts.md#755-accessibility-constraints)).
 
-The *method_body* of a returns-by-value or returns-no-value method is either a semicolon, a ***block body*** or an ***expression body***. A block body consists of a *block*, which specifies the statements to execute when the method is invoked. An expression body consists of `=>`, followed by a *null_conditional_invocation_expression* or *expression*, and a semicolon, and denotes a single expression to perform when the method is invoked.
+The *method_body* of a returns-by-value or returns-no-value method is either a semicolon, a block body or an expression body. A block body consists of a *block*, which specifies the statements to execute when the method is invoked. An expression body consists of `=>`, followed by a *null_conditional_invocation_expression* or *expression*, and a semicolon, and denotes a single expression to perform when the method is invoked.
 
 For abstract and extern methods, the *method_body* consists simply of a semicolon. For partial methods the *method_body* may consist of either a semicolon, a block body or an expression body. For all other methods, the *method_body* is either a block body or an expression body.
 
 If the *method_body* consists of a semicolon, the declaration shall not include the `async` modifier.
 
-The *ref_method_body* of a returns-by-ref method is either a semicolon, a ***block body*** or an ***expression body***. A block body consists of a *block*, which specifies the statements to execute when the method is invoked. An expression body consists of `=>`, followed by `ref`, a *variable_reference*, and a semicolon, and denotes a single *variable_reference* to evaluate when the method is invoked.
+The *ref_method_body* of a returns-by-ref method is either a semicolon, a block body or an expression body. A block body consists of a *block*, which specifies the statements to execute when the method is invoked. An expression body consists of `=>`, followed by `ref`, a *variable_reference*, and a semicolon, and denotes a single *variable_reference* to evaluate when the method is invoked.
 
 For abstract and extern methods, the *ref_method_body* consists simply of a semicolon; for all other methods, the *ref_method_body* is either a block body or an expression body.
 
@@ -3170,7 +3170,7 @@ The *member_name* ([§15.6.1](classes.md#1561-general)) specifies the name of th
 
 The *type* of a property shall be at least as accessible as the property itself ([§7.5.5](basic-concepts.md#755-accessibility-constraints)).
 
-A *property_body* may either consist of a ***statement body*** or an ***expression body***. In a statement body,  *accessor_declarations*, which shall be enclosed in “`{`” and “`}`” tokens, declare the accessors ([§15.7.3](classes.md#1573-accessors)) of the property. The accessors specify the executable statements associated with reading and writing the property.
+A *property_body* may either consist of a statement body or an expression body. In a statement body,  *accessor_declarations*, which shall be enclosed in “`{`” and “`}`” tokens, declare the accessors ([§15.7.3](classes.md#1573-accessors)) of the property. The accessors specify the executable statements associated with reading and writing the property.
 
 In a *property_body* an expression body consisting of `=>` followed by an *expression* `E` and a semicolon is exactly equivalent to the statement body `{ get { return E; } }`, and can therefore only be used to specify read-only properties where the result of the get accessor is given by a single expression.