Struct nesting / flattening randomization

[abaresk]

Nesting

The permuter should be able to create substructs by nesting fields from a larger struct. For example:

typedef struct {
  int foo;
  int bar;
  int baz;
} FooBarBaz;

can become

typedef struct {
  int foo;
  int bar;
} FooBar;

typedef struct {
  FooBar foobar;
  int baz;
} FooBarBaz;

Flattening

Similarly, the permuter should be able to flatten fields from a nested struct. After selecting the substruct, it should attempt to either flatten some of the upper fields upwards or some of the lower fields downwards. For example:

typedef struct {
  int foo;
  int bar;
  int baz;
} FooBarBaz;

typedef struct {
  FooBarBaz fooBarBaz;
  int qux;
} FooBarBazQux;

can become

typedef struct {
  int bar;
  int baz;
} BarBaz;

typedef struct {
  int foo;
  BarBaz barBaz;
  int qux;
} FooBarBazQux;

or it could become

typedef struct {
  int foo;
  int bar;
} FooBar;

typedef struct {
  FooBar fooBar;
  int baz;
  int qux;
} FooBarBazQux;