apps/nshlib: The I/O buffer, g_iobuffer, should not be a global buffer. That...

apps/nshlib:  The I/O buffer, g_iobuffer, should not be a global buffer.  That will not work in an environment where there are multiple NSH sessions.  The I/O buffer must, instead, be a part part of the session-specific data defined in nsh_console.h # Please enter the commit message for your changes. Lines starting # with '#' will be ignored, and an empty message aborts the commit.