Some code improvement or cleaning.
- debug.js: LogFile is a local var
- dom_funcs.js: RegExps improved
- globals.js: ihg_Globals.logFile obsolete, becomes ihg_Globals.LocalFile for futur use
- host_funcs.js: 'function' Search Pattern decoded with more relevance regarding arguments
- imagegrabber.js: code 'cleaning'
- update.js: code 'cleaning'
- utils.js: String.trim() and JSON support for FF<3.5; imagevenue rename improved
- downloads.xul: debug and console prefs @ startup taken into account
- options.xul: debug and console prefs @ startup taken into account
- overlay.js: debug and console prefs @ startup taken into account
- filter: code cleaned and optimized

Signed-off-by: Rookie <Thierry@pb>