rs6000: use li;x?oris to build constant

rs6000: use li;x?oris to build constant

For constant C:
If '(c & 0xFFFFFFFF00008000ULL) == 0xFFFFFFFF00008000ULL' or say:
32(1) || 16(x) || 1(1) || 15(x), using "li; xoris" would be ok.

If '(c & 0xFFFFFFFF80008000ULL) == 0x80000000ULL' or say:
32(0) || 1(1) || 15(x) || 1(0) || 15(x), we could use "li; oris" to
build constant 'C'.

Here N(M) means N continuous bit M, x for M means it is ok for either
1 or 0; '||' means concatenation.

This patch update rs6000_emit_set_long_const to support those constants.

	PR target/106708

gcc/ChangeLog:

	* config/rs6000/rs6000.cc (rs6000_emit_set_long_const): Add using
	"li; x?oris" to build constant.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr106708.c: New test.