Rizin has a command injection via RzBinInfo bclass due legacy code

Rizin is a UNIX-like reverse engineering framework and command-line toolset. `rizin.c` still had an old snippet of code which suffered a command injection due the usage of `rz_core_cmdf` to invoke the command `m` which was removed in v0.1.x. A malicious binary defining `bclass` (part of RzBinInfo) is executed if `rclass` (part of RzBinInfo) is set to `fs`; the vulnerability can be exploited by any bin format where `bclass` and `rclass` are user defined. This vulnerability is fixed in 0.7.4.