[MPlayer-DOCS] Improvement to README for 64 bit essentials

[Wolfgang Knauf]

Hi everybody,

I suggest an improvement to the file "README", section "STEP1: 
Installing Binary Codecs".
Add something like this:
"For 64 bit linux: first place the 32 bit essentials in the binary codes 
directory, then replace the 32 bit libraries with the 64 bit versions 
from the 64 bit essentials package."

This small hint might have prevented a silly noob like me from compiling 
a 32 bit MPlayer, because a real media file caused a "wrong ELF32_CLASS" 
error in a 32 bit codec ;-).

Thanks

Wolfgang