pgmapcss_parse_string(): new function, read string from current input
pgmapcss_parse_string(): return (null,0) on failure
pgmapcss_condition()/pgmapcss_parse_selector(): use pgmapcss_parse_string

-> more advanced characters possible
pgmapcss_parse_selector(): Handle object class '*'
pgmapcss_build_statement(): Bugfix, no conditions -> if(true)
pgmapcss_parse_string: optionally add offset
pgmapcss_parse_eval(): parse content of eval(...) statement
pgmapcss_parse_eval(): parse text into a tree
Basic support for eval(...)
pgmapcss_parse_eval(): Bugfix parsing operations
pgmapcss_parse_properties(): Bugfix reading eval() statements
pgmapcss_parse_properties(): support eval("....")
pgmapcss_parse_eval(): Applied a lot of magic tape to make it work - hopefully
Compile eval(...); Add basic eval-functions + documentation
Eval: improve documentation; add 'sqrt', 'boolean', 'concat', 'any'
Eval: Add >, >=, <=, <, cond()
Eval: function number()
Update MapCSS documentation (support eval() expressions)