nasmlib.c: Make nasm_opt_val robust
nasmlib.c: Make nasm_opt_val robust

nasm_opt_val should be able handle various text stream
passed, including tainted ones. Make it so.

Also it fixes the case when Elf section has multiple
attributes such as "progbits align=16" and friends
(introduced by commit bb0745f). The former just ignore
any other options/values except first one.

Signed-off-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@gmail.com>

projedi/nasm,turingstudio/nasm,turingstudio/nasm,techkey/nasm,turingstudio/nasm,projedi/nasm,letolabs/nasm,Distrotech/nasm,letolabs/nasm,projedi/nasm,projedi/nasm,techkey/nasm,turingstudio/nasm,techkey/nasm,letolabs/nasm,Distrotech/nasm,Distrotech/nasm,techkey/nasm,projedi/nasm,techkey/nasm,Distrotech/nasm