Clean up of Fortran back end
1, to make it clean, map all user defined functions in MATLAB to
subroutines in Fortran;
2, added runtime allocations, check out getCurrentShape method in
HandleCaseTIRAbstractAssignToListStmt class;
3, according to conventions of Fortran, change all the intrinsic
procedures and keywords to uppercase;
4, only do constant removal for temporary variables which are
generated during tamer analysis, leave user defined constatn vars;
5, not declare those index vars or loop vars as integer in the
declaration section, but put intrinsic function "int()" when using
them in indexing or loop condition, for example:
                    do i = int(a) , int(b)
this will be more similar to the way MATLAB does.

TODO to separate linear indexing transformation from other rigorous
indexing transformation, to support polymorphism or type conflict
by using derived type (union type) in Fortran, and to support struct
and cell arrays (also by union type).
remove a file