gstrfuncs: use gsize type internally for strv functions
gstrfuncs: use gsize type internally for strv functions

In C, the proper type for a heap allocate structure is size_t/gsize.
That means, no valid (heap allocated) pointer will ever contain more
bytes than size_t can represent.

Hence, this integer type should also be used when operating on
data like a strv array. Adjust some internal uses to use gsize
instead of gint/guint.

Note that g_strv_length() returns a value of type guint. So this
API cannot be used on string arrays longer of arbitrary size. But
that is not fixable.

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib