Basic struct definition support

[ForNeVeR]

Cesium should support basic struct definitions required for #61. For example, this:

/* The SHA-1 context. */
typedef struct {
	uint64_t total;
	uint32_t ihv[5];
	unsigned char buffer[64];
	int found_collision;
	int safe_hash;
	int detect_coll;
	int ubc_check;
	int reduced_round_coll;
	collision_block_callback callback;

	uint32_t ihv1[5];
	uint32_t ihv2[5];
	uint32_t m1[80];
	uint32_t m2[80];
	uint32_t states[80][5];
} SHA1_CTX;

Subtasks:

• struct with primitive fields
• unsigned char
• (suddenly) functional type:

  typedef void(*collision_block_callback)(uint64_t, const uint32_t*, const uint32_t*, const uint32_t*, const uint32_t*);

• primitive fixed arrays
• primitive multi-dimensional arrays

Depends on:

• Function parameters with abstract declarators #234 (because of the collision_block_callback depending on it, actually)