support blockquote tag.
libsylph/html.c: minor code cleanup.
html.c: style end tags search fix.
supported <br/> HTML tag.
look at every attribute in 'a' tag for 'href' (thanks to Rich Coe).
libsylph/html.c: improved entity references conversion.
changed the license of LibSylph from GPL to LGPL.
fixed signedness warnings.
moved html.[ch] to libsylph.