Use two 64 bit values for f128 Softfloat interface

Author: jordancarlin

c_emulator/riscv_sail.h

@@ -64,8 +64,7 @@ extern mach_bits zmstatus;
 extern mach_bits zmepc, zmtval;
 extern mach_bits zsepc, zstval;
 
-extern mach_bits zfloat_fflags;
-extern sail_bits zfloat_result;
+extern mach_bits zfloat_fflags, zfloat_result, zfloat_result_high;
 
 struct zMcause {
   mach_bits zMcause_chunk_0;