Added the completion of the macro's name.

Added the completion of the macro's name.
To meet this goal, the abstract lexer has a new method: complete.
T(L)PushLexer doesn't implement this method. But there are two additional
classes: ITPushLexer and ILPushLexer. These are derived from TPushLexer and
LPushLexer. The only difference between the derived classes and their parents
is the implementation of the method complete.
TDictionary has a new method: complete. It's used by the lexers.
Now, in LPushLexer, long identifiers can be composed by these additional
character: '-' and '_'. To insert them as part of long identifiers, the
user has escape them with '\'.
Added a new node in the TML tree. It' name is 's' and represents a space.
It can be pushed only with a LPushLexer.