fileapi: Use unsigned int consistently for version numbers

The file API code used unsigned long to hold the major version in most
places, but not all. Some places used unsigned int, and an important one
of those is the cmFileApi::BuildVersion() function. As a result, it has never
been safe for a large value not representable by an unsigned int to be
used in these variables.

Convert all of the file API version number variables and function arguments
to use unsigned int consistently. This avoids any size mismatch warnings
when passing values around. They also don't need to be unsigned long,
as we never expect version numbers to be anything even close to what
an unsigned int cannot represent.

Source/cmMessageCommand.cxx

@@ -69,7 +69,7 @@ void WriteMessageEvent(cmConfigureLog& log, cmMakefile const& mf,
                        std::string const& message)
 {
   // Keep in sync with cmFileAPIConfigureLog's DumpEventKindNames.
-  static std::vector<unsigned long> const LogVersionsWithMessageV1{ 1 };
+  static std::vector<unsigned int> const LogVersionsWithMessageV1{ 1 };
 
   if (log.IsAnyLogVersionEnabled(LogVersionsWithMessageV1)) {
     log.BeginEvent("message-v1", mf);