Review usage of Reporter::InternalError, addresses BIT-1045.

Replaced some with InternalWarning or InternalAnalyzerError, the later
being a new method which signals the analyzer to not process further
input.  Some usages I just removed if they didn't make sense or clearly
couldn't happen.  Also did some minor refactors of related code while
reviewing/exploring ways to get rid of InternalError usages.

Also, for TCP content file write failures there's a new event:
"contents_file_write_failure".

src/Reporter.h

@@ -12,6 +12,7 @@
 #include "EventHandler.h"
 #include "IPAddr.h"
 
+namespace analyzer { class Analyzer; }
 class Connection;
 class Location;
 class Reporter;
@@ -91,6 +92,10 @@ public:
 	// dump after the message has been reported.
 	void InternalError(const char* fmt, ...) FMT_ATTR;
 
+	// Reporter an internal analyzer error.  That analyzer will not process
+	// any further input, but Bro otherwise continues normally.
+	void InternalAnalyzerError(analyzer::Analyzer* a, const char* fmt, ...);
+
 	// Toggle whether non-fatal messages should be reported through the
 	// scripting layer rather on standard output. Fatal errors are always
 	// reported via stderr.