mxqsub allows submission of commands containing whitespaces in command names

[mariux]

this leads to unparsable mxqdump output..

solution:

• either disallow commands with whitespaces
• or fix mxqdump output

in addition fix silent truncation of --command-alias arguments that contain whitespaces

[mariux]

• disallow whitespaces in command-alias
• disallow whitespaces in argv[0] if command-alias is not used