Cleaning todo

The order is not significative.

Macros
M1.- Remove NOT_USED_OR_REPLACED Macro
M2.- Remove PYXIS macro
M3.- Remove NO_CHECKSUM macro (and CCH_Checksum function in cch.cpp)
M4.- Remove GDS_VAL and GDS_REF macros.
M5.- Remove NULL_PTR macro
M6.- Remove BOOLEAN, TRUE and FALSE macros and replace with keywords.
M7.- Remove TEXT and SCHAR macros.

Code
C1.- Remove warnings (excluding parentheses, unused var, non complete switches and pragmas)
C2.- Define (type-safe?) unions for nod_arg and lls_object. 
	Nod_arg is used in several places of the code to contain pointers to several kinds of objects or numbers, whether is defined as pointer to xxx_nod.
	The same happends with lls_object in lls (linked list) where the lls_object can store pointers or numbers, whether is defined as pointer to xxx_nod.
	See gpre.h nod_arg in gpre_nod struct and lls_object in lls struct.
C3.- Modify gds__msg_format and derivated functions to use arglist instead of TEXT arguments. This change will also remove a lot of casts.
C4.- Remove casts.
C5.- Replace macros with code with inline? functions.
C6.- Assertion cleaning. Now there are in the code compiler and custom assertions.

Builds
B1.- Posix take cpp generated from epp out of src directory.
B2.- Build help.fdb from script.
B3.- Build msg.fdb from script.


The point C1 is prepared and will be committed when 1.5 is out.