Font lock `define-syntax-rule' like `define' procedures

`define-syntax-rule' is similar enough to procedure definitions that
it should be highlight as a slightly different version of one.

The faces were chosen to keep the same scheme used by `define-macro'.

`define-syntax-rule' was removed from Racket's extra keywords as there
is no need to special case it.
Using font-lock-function-name-face for define-syntax-rule

The name defined It's more like a function in a define than a variable,
since it can take arguments.