powerman: increase maximum line length

Problem: On very larger clusters command line operations of a large
number of nodes (e.g. node[1,3,5,...,4997,4999]) can exceed internal
buffers, leading to errors.

Increase the internal maximum line length from 8K to 128K, which should
handle any HPC cluster in existence today and larger ones in the future.

Fixes #193

src/powerman/client_proto.h

@@ -21,7 +21,7 @@
  * If not quit, goto 3
  */
 
-#define CP_LINEMAX  8192                /* max request/response line length */
+#define CP_LINEMAX  131072              /* max request/response line length */
 #define CP_EOL      "\r\n"              /* line terminator */
 #define CP_PROMPT   "powerman> "        /* prompt */
 #define CP_VERSION  "001 %s" CP_EOL