change the location_t type, DECL_SOURCE_LINE etc

[Per Bothner]

Ignore the proposal below for now, until Neil and I figure
out if we can add column number support to the line-map stuff.
Perhaps that can solve the goal below, while avoid the hard
limit on the number of files - plus making use of the
existing code.  Let's see what Neil says.

Per Bothner wrote:

> This is a revised proposal for compressing file/line/[column]
> numbers into 32 bits, but it can handle very large files.
>
> Motivation/goals:
> * Shrink location_t down to 32 bits.
> * Handle column numbers, at least for reasonably-sized files.
> * Handle huge files, though not necessarily with column numbers.
> * Handle a large but not huge (specifically 4095) number of source files.


-- 
	--Per Bothner
per@bothner.com   http://www.bothner.com/per/