Interoperability with C int128_t type?

[Sa Liu]

I have been reading the chapter Interoperability with C in Fortran 
Standard, and found that for the intrinsic types, there is no support for 
the C type int128_t. 
This is an optional arithmetic type and some platforms do support 128 bit 
integer. 
Is that possible to extend Gfortran to add a new C interoperable type 
C_INT128_T?

Thanks!
Sa