[BRIGFE] Reduce the number of type conversions due to

[BRIGFE] Reduce the number of type conversions due to
the untyped HSAIL regs.

Instead of always representing the HSAIL's untyped registers as
unsigned int, the gccbrig now pre-analyzes the BRIG code and
builds the register variables as a type used the most when storing
or reading data to/from each register. This reduces the total
conversions which cannot be always optimized away.

From-SVN: r254837