Rename variable in TARGA image handler.

Current name of the variable ('index') is misleading. Actually it represents number of bytes created on output so 'outputLength' name seems to be more relevant.

src/common/imagtga.cpp

@@ -105,12 +105,12 @@ static
 int DecodeRLE(unsigned char* imageData, unsigned long imageSize,
                short pixelSize, wxInputStream& stream)
 {
-    unsigned long index = 0;
+    unsigned long outputLength = 0;
     unsigned char current;
     unsigned int length;
     unsigned char buf[4];
 
-    while (index < imageSize)
+    while (outputLength < imageSize)
     {
         int ch = stream.GetC();
         if ( ch == wxEOF )
@@ -128,9 +128,9 @@ int DecodeRLE(unsigned char* imageData, unsigned long imageSize,
 
             length = current;
 
-            index += current * pixelSize;
+            outputLength += current * pixelSize;
 
-            if (index > imageSize)
+            if (outputLength > imageSize)
             {
                 return wxTGA_IOERR;
             }
@@ -153,9 +153,9 @@ int DecodeRLE(unsigned char* imageData, unsigned long imageSize,
 
             length = current * pixelSize;
 
-            index += length;
+            outputLength += length;
 
-            if (index > imageSize)
+            if (outputLength > imageSize)
             {
                 return wxTGA_IOERR;
             }