Port of WebPConv.

Big thankyou to Michael Trebilcock for his port of libvpx which
made this possible.

2nd release - dynamically linked against libvpx 0.9.2
Copy SObjs to SObjs:
makelink sobjs:libvpx.so.0 sobjs:libvpx.so.0.9.2

(if you have installed the datatype then the link will already be done)

 PERMSSN    UID  GID    PACKED    SIZE  RATIO METHOD CRC     STAMP          NAME
---------- ----------- ------- ------- ------ ---------- ------------ -------------
[generic]                  774    1495  51.8% -lh5- 5c0e Sep 29 18:15 libwebp/LICENSE
[generic]                 1216    2872  42.3% -lh5- 8e79 Oct  3 17:50 libwebp/makefile
[generic]                  633    1295  48.9% -lh5- 653c Sep 29 18:15 libwebp/PATENTS
[generic]                  262     395  66.3% -lh5- eb19 Sep 29 18:15 libwebp/README
[generic]               449309 1181596  38.0% -lh5- 292f Aug 24 20:15 libwebp/SObjs/libjpeg.so.8
[generic]               186538  462369  40.3% -lh5- f7a3 Oct  3 14:21 libwebp/SObjs/libvpx.so.0.9.2
[generic]               566633 1445015  39.2% -lh5- 025b Oct  3 17:51 libwebp/webpconv
[generic]                 2715    8653  31.4% -lh5- 8bda Sep 29 18:19 libwebp/webpconv.c
[generic]                  364     608  59.9% -lh5- cf83 Oct  3 18:00 libwebp/webpconv.readme
[generic]                 7228   26304  27.5% -lh5- fd8c Oct  2 13:46 libwebp/webpimg.c
[generic]                 3158    5120  61.7% -lh5- 198c Oct  2 12:20 libwebp/webpimg.c.info
[generic]                 2062    7234  28.5% -lh5- d021 Oct  2 11:55 libwebp/webpimg.h
[generic]                 3162    5120  61.8% -lh5- d9c4 Oct  1 22:11 libwebp/webpimg.h.info
---------- ----------- ------- ------- ------ ---------- ------------ -------------
 Total        13 files 1224054 3148076  38.9%            Oct  3 20:27