used to reduce the amount of heap size required to only test wether
we're dealing with a BDF font (the old code allocated 64 Kb right
before any test).
* src/lzw/ftlzw.c (FT_Stream_OpenLZW): modified the function to check
the LZW header before doing anything else. This helps avoid un-necessary
heap allocations (400 Kb of heap memory for the LZW decoder ! Oh my !)
* src/gzip/ftgzip.c (FT_Stream_OpenGZip): ditto for the .gz decoder,
though the code savings is smaller.