fix limitation for size of data:*:base64 images and max length of the html input line

[Shaeto]

trafficstars

1. currently maximum size of <img ... src='data:...:base64.....' ..> image is ~7k
2. maximum length of input line for input html document is 10240 (limited by code in htmllib.cxx)

this patch removes these limitations

test command is:

cat ./test.html | htmldoc --webpage -t pdf - > test.pdf

test.html is attached

test.html.zip