Make company-backends buffer-local?

[Jefferson Carpenter <jeffersoncarpenter2@gmail.com>]

First post to this list -- sorry if this is either not a good suggestion 
at all, not right format, or too irrelevant.

The company-backends variable is currently a global variable.  The 
backend that serves completions is the first one that returns a prefix 
for the location at point.

Are there any barriers to making company-backends a buffer-local 
variable?  I don't see any drawbacks - it would take a pretty small 
amount of extra memory to create a copy for each buffer.  The advantages 
include:

1: You can specify backends mode by mode.  I at least feel this makes 
far more sense philosophically.

2: Would fix a possible issue where a backend at the beginning of the 
list is actually for a different file type - maybe for a similar 
language, say Java vs C++ - however still happens to return a prefix, 
and subsequently doesn't return any of the right completions.

3 (extremely minor): Might speed up completions for backends that were 
at the end of the list, since each mode can be programmed with a 
specific list of backends.

TY,
Jefferson Carpenter