[binutils-gdb] read/write_pieced_value: Improve logic for buffer allocation

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 242d31ab7c3901e02bd68c1824d1d3610e02562b ***

Author: Andreas Arnez <arnez@linux.vnet.ibm.com>
Branch: master
Commit: 242d31ab7c3901e02bd68c1824d1d3610e02562b

read/write_pieced_value: Improve logic for buffer allocation

So far the main loop in read_pieced_value and write_pieced_value is
structured like this:

(1) Prepare a buffer and some variables we may need;

(2) depending on the DWARF piece type to be handled, use the buffer and
    the prepared variables, ignore them, or even recalculate them.

This approach reduces readability and may also lead to unnecessary copying
of data.  This patch moves the preparations to the places where sufficient
information is available and removes some of the variables involved.

gdb/ChangeLog:

	* dwarf2loc.c (read_pieced_value): Move the buffer allocation and
	some other preparations to the places where sufficient information
	is available.
	(write_pieced_value): Likewise.