fix DEBUG_IN_C for linux

warn when readline.so is not found, or pn_readline()
change the debug loop status values: 5,6 for :q,:exit
!DEBUG_IN_C global Debug class

change the debug loop status values: 5,6 for :q,:exit
syntax: move yylastline from compile to syntax*.y and G->line to P

return P->line as Bytes directly, without intermediate G
and malloc'd and free'd char* buffers.