* remote.c: Improve error recovery. Allow user to break out

* remote.c:  Improve error recovery.  Allow user to break out
of initial connection attempt with INTERRUPT.  Treat a timeout
while waiting for remote packet like a retry, unless the remote
side is actively running user code.  Fix a few long printf_filtered's.

* xcoffread.c (read_xcoff_symtab):  Don't use null symbol name for
trampoline symbols.

* buildsym.c (start_subfile):  Allow null file name.