Call select() before reading from the child.

In readFromChild() for non-Windows: Call select() to check
for available data.  Reason: To ensure that ::read() doesn't
hang if the child exits during the call to ::read().

child.cpp

@@ -1525,6 +1525,29 @@ namespace CodeDweller {
 
       }
 #else
+      fd_set readFd;
+      int retVal;
+      struct timeval timeout = {0, 0};
+
+      FD_ZERO(&readFd);
+      FD_SET(inputFileDescriptor, &readFd);
+
+      // Check if input is available.
+      retVal = select(inputFileDescriptor + 1, &readFd, NULL, NULL, &timeout);
+
+      if (-1 == retVal) {
+	throw std::runtime_error("Error from select() when reading from the "
+				 "child process: " + getErrorText());
+      }
+
+      // Is data available?
+      if (0 == retVal) {
+
+	// No.  Wait and try again.
+	pollTimer.pause();
+	continue;
+      }
+
       ssize_t nBytesRead;
 
       nBytesRead = ::read(inputFileDescriptor,