some improvements to emails.d decoders (after testing against 100.000+ emails)
fixed this compile error on htmltotext.d:

htmltotext.d(64): Error: function arsd.htmltotext.repeat (string s, int num) is not callable using argument types (string, ulong)
htmltotext.d(69): Error: function arsd.htmltotext.repeat (string s, int num) is not callable using argument types (string, ulong)