[PATCH 0/4][MSP430] Improve behaviour of ".either" section placement

[Jozef Lawrynowicz]

GCC for the MSP430 target has a feature that allows the user to specify
which memory region to place code and/or data in, using the -mcode-
region and -mdata-region options.
MSP430 devices with a high memory region support this placement of
code/data by defining ".upper" and ".lower" output sections in linker
scripts.
The parameters that can be passed to -mcode/data-region are "none",
"upper", "lower", "either". The use of the "either" option requires some
work to be done by the linker, to place ".either" code and data sections
in either the upper or lower regions to prevent memory region overflow,
if possible. The following patches improve and fix some of the existing
behaviour of this ".either" placement functionality.