sysutils/fusefs-sshfs: fix build on GCC architectures

Use C11 compiler:
../sshfs.c:3842: error: expected '=', ',', ';', 'asm' or 'attribute' before '{' token
../sshfs.c:3878: error: expected '=', ',', ';', 'asm' or 'attribute' before '{' token
../sshfs.c:3897: error: expected '=', ',', ';', 'asm' or 'attribute' before '{' token
../sshfs.c:3927: error: expected '=', ',', ';', 'asm' or 'attribute' before '{' token
../sshfs.c:3944: error: expected '=', ',', ';', 'asm' or 'attribute' before '{' token