Fix assorted compiler warnings found by Clang

simgear/misc/sg_path.cxx

@@ -206,7 +206,7 @@ string SGPath::base() const
         return path;
     }
     
-    if (index >= 0) {
+    if (index != string::npos) {
         return path.substr(0, index);
     } else {
         return path;
@@ -256,7 +256,7 @@ string SGPath::complete_lower_extension() const
     }
     
     string::size_type firstDot = path.find(".", index);
-    if ((firstDot >= 0)  && (path.find(sgDirPathSep, firstDot) == string::npos)) {
+    if ((firstDot != string::npos)  && (path.find(sgDirPathSep, firstDot) == string::npos)) {
         return boost::to_lower_copy(path.substr(firstDot + 1));
     } else {
         return "";

simgear/misc/sg_path.hxx

@@ -124,7 +124,7 @@ public:
     std::string dir() const;
   
     /**
-     * Get the base part of the path (everything but the extension.)
+     * Get the base part of the path (everything but the final extension.)
      * @return the base string
      */
     std::string base() const;

simgear/misc/zfstream.cxx

@@ -167,7 +167,7 @@ gzfilebuf::close()
 
 
 std::streampos
-gzfilebuf::seekoff( std::streamoff, ios_seekdir, int )
+gzfilebuf::seekoff( std::streamoff, ios_seekdir, ios_openmode )
 {
     return std::streampos(EOF);
 }

simgear/misc/zfstream.hxx

@@ -90,7 +90,7 @@ public:
     bool is_open() const { return (file != NULL); }
 
     /** @return stream position */
-    virtual std::streampos seekoff( std::streamoff off, ios_seekdir way, int which );
+    virtual std::streampos seekoff( std::streamoff off, ios_seekdir way, ios_openmode which );
 
     /** sync the stream */
     virtual int sync();