gdb, fortran: Fix quad floating-point type for ifort compiler.

gdb, fortran: Fix quad floating-point type for ifort compiler.

I fixed this a while ago for ifx, one of the two Intel compilers, in
8d624a9d8050ca96e154215c7858ac5c2d8b0b19.

Apparently I missed that the older ifort Intel compiler actually emits
slightly different debug info again:

0x0000007a:   DW_TAG_base_type
                DW_AT_byte_size	(0x20)
                DW_AT_encoding	(DW_ATE_complex_float)
                DW_AT_name	("COMPLEX(16)")

0x00000081:   DW_TAG_base_type
                DW_AT_byte_size	(0x10)
                DW_AT_encoding	(DW_ATE_float)
                DW_AT_name	("REAL(16)")

This fixes two failures in gdb.fortran/complex.exp with ifort.

Approved-By: Tom Tromey <tom@tromey.com>