(svn r2290) - CodeChange: protect the next batch of commands. This brings us to a total of 61, which is 53% :)
- CodeChange: To correctly accept engine-prototypes, the best-player checking has been moved to its own function, I hope it functions the same as before.
- CodeChange: Added symbolic types of PlayerID, OrderID and EngineID. For engines also added GetEngine() and IsEngineIndex(), similar to the other such functions.
- CodeChange: To correctly build industries, some tables have been moved to build_industry.h. The only way to find out currently if an industry is valid in a climate is by looping all industries and checking if it matches. Also to comply with the patch setting build_rawmaterial_industries, it is assumed that these industries do not accept any cargo of any type. This can and probably should changed in the future to some flag in their struct. Also use _opt_ptr instead of _opt.
- CodeChange: implemented the HQ checking code inspired by MarkR2 in "[ 1190944 ] Many commands not checked for security". Unfortunately it is impossible to prevent only deleting a HQ by a modified client atm.
- CodeChange: For insert order and modify order their parameters are implicitely truncated to 8 bits, instead of the 16 bits said in the comments.

#ifndef SIGNS_H
#define SIGNS_H

#include "pool.h"

typedef struct SignStruct {
	StringID     str;
	ViewportSign sign;
	int32        x;
	int32        y;
	byte         z;
	byte owner; // placed by this player. Anyone can delete them though.
							// OWNER_NONE for gray signs from old games.

	uint16       index;
} SignStruct;

extern MemoryPool _sign_pool;

/**
 * Check if a Sign really exists.
 */
static inline bool IsValidSign(SignStruct* ss)
{
	return ss->str != 0;
}

/**
 * Get the pointer to the sign with index 'index'
 */
static inline SignStruct *GetSign(uint index)
{
	return (SignStruct*)GetItemFromPool(&_sign_pool, index);
}

/**
 * Get the current size of the SignPool
 */
static inline uint16 GetSignPoolSize(void)
{
	return _sign_pool.total_items;
}

#define FOR_ALL_SIGNS_FROM(ss, start) for (ss = GetSign(start); ss != NULL; ss = (ss->index + 1 < GetSignPoolSize()) ? GetSign(ss->index + 1) : NULL)
#define FOR_ALL_SIGNS(ss) FOR_ALL_SIGNS_FROM(ss, 0)

VARDEF SignStruct *_new_sign_struct;

VARDEF bool _sign_sort_dirty;
VARDEF uint16 *_sign_sort;

void UpdateAllSignVirtCoords(void);
void PlaceProc_Sign(uint tile);

/* misc.c */
void ShowRenameSignWindow(SignStruct *ss);

#endif /* SIGNS_H */