[Linux][Gnuplot][輸出 PDF 檔 by PDFLite]

1. Download PDFlib Lite (http://www.pdflib.com/download/pdflib-family/pdflib-lite-7/)
2. tar zxf PDFlib-Lite-xx.tar.gz
3. cd PDFlib-Lite-xx && ./configure && make
4. sudo make install
5. sudo ldconfig
6. Reinstall gnuplot