Replace signal with sigaction

[Alex Toader]

The manual states:

 The only portable use of signal() is to set a signal's disposition to SIG_DFL or  SIG_IGN.   The  semantics when  using signal() to establish a signal handler vary across systems (and POSIX.1 explicitly permits this variation); do not use it for this purpose.
 POSIX.1 solved the portability mess by specifying sigaction(2), which  provides  explicit  control  of  the semantics when a signal handler is invoked; use that interface instead of signal().

Whenever you see a call to signal in the code, replace it with sigaction.

[Dimitar Misev]

Should be fixed in these files (search for 'signal('):

applications/rasql/rasql_signal.cc
applications/directql/directql_signal.cc
clientcomm/rpcclientcomm.cc
rasmgr_x/src/main.cc
servercomm/manager.cc
servercomm/servercomm.cc
servercomm/httpserver.cc
server/rasserver_main.cc
rnprotocol/rnpserver.cc