Fix compilation, if zlib-1.2.6 is installed
Source:
http://permalink.gmane.org/gmane.science.robotics.playerstage.user/12380

--- server/drivers/shell/readlog.cc.old	2012-05-23 21:52:12.202203918 +0200
+++ server/drivers/shell/readlog.cc	2012-05-23 21:53:25.088198126 +0200
@@ -665,7 +665,7 @@
       // back up to the beginning of the file
 #if HAVE_Z
       if (this->gzfile)
-        ret = gzseek(this->file,0,SEEK_SET);
+        ret = gzseek((gzFile)this->file,0,SEEK_SET);
       else
         ret = fseek(this->file,0,SEEK_SET);
 #else
@@ -711,7 +711,7 @@
       // compared to fgets (on uncompressed files), so use the latter.
 #if HAVE_Z
       if (this->gzfile)
-        ret = (gzgets(this->file, this->line, this->line_size) == NULL);
+        ret = (gzgets((gzFile)this->file, this->line, this->line_size) == NULL);
       else
         ret = (fgets(this->line, this->line_size, (FILE*) this->file) == NULL);
 #else