This patch adds a list of strings called 'ctor_of' to
_Eolian_Function. This list will contain all classes in which this
function is a constructing function.
ctor_of is filled in two moments:
* When filling the constructors of a class, class->full_name is inserted
in the 'ctor_of' of each constructor's function.
* When filling the implements of a class, if the function is a
constructor of its superclass it also becomes a constructor of the
current class, so class->full_name is also inserted in the 'ctor_of'
of each implement's function.
eolian_function_is_constructor gets a func and klass arguments. It goes
through ctor_of of func and returns EINA_TRUE if klass->full_name is
found, otherwise it returns EINA_FALSE.
This commit also does several side (related) changes. Particularly, it updates
the Eolian C generator to use the new API, it adds missing expr types (null, char)
and masks, updates the API dealing with default return values to use expressions
instead of strings and does several fixes (mainly in lexer) around the place.
It also disallows single quoted strings as those are reserved for characters.