ruby: slicc: improve the grammar

ruby: slicc: improve the grammar
This patch changes the grammar for SLICC so as to remove some of the
redundant / duplicate rules.  In particular rules for object/variable
declaration and class member declaration have been unified. Similarly, the
rules for a general function and a class method have been unified.

One more change is in the priority of two rules.  The first rule is on
declaring a function with all the params typed and named.  The second rule is
on declaring a function with all the params only typed.  Earlier the second
rule had a higher priority.  Now the first rule has a higher priority.