libgcc_s: Export 64-bit int to 128-bit float functions

[jrtc27]

Summary

The corresponding 32-bit int and 128-bit int functions were added in
790a6be5a169, as were all combinations of the float to int functions,
but these two were overlooked. __floatditf is needed to build curl for
riscv as there's a signed 64-bit int to 128-bit float conversion in
lib/progress.c's trspeed as of 7.77.0.

MFC after: 1 week

[dim]

LGTM, thanks!