* cppexp.c: When forcing unsigned comparisons, cast both sides
        of the operation.
        * cpphash.h: Move static declaration of hashtab[]...
        * cpphash.c: ...here.
        * cpplib.c: Cast difference of two pointers to size_t before
        comparing it to size_t.  Cast signed to unsigned
        before comparing to size_t. (FIXME: struct argdata should use
        unsigned buffer sizes.)
        * cpplib.h (struct cpp_reader): Declare token_buffer_size as
        unsigned int. (CPP_WRITTEN): Cast return value to size_t.
        (CPP_RESERVE): Parenthesize N for evaluation order, cast to
        size_t before comparison.

From-SVN: r22980