asm_stats crash when parsing RV32F/D instructions with "." in opcode

[nibrunieAtSi5]

reported by Hugues
$ python3 -m asmde.asm_stats --arch rv32 --input examples/riscv/test_rv32_f.S
parsing input program examples/riscv/test_rv32_f.S
unable to parse [Lexem(fadd), OperatorLexem(.), Lexem(s), Lexem(f2), Lexem(f2), Lexem(f0)] @ line 5, head=Lexem(fadd)

[nibrunie]

This should be solved for assembly file by #9 adding support for "--mode asm". However it will not solve the issue for objdump file with F/D extension instructions.