rs6000: Fix signed integer overflows

bootstrap-ubsan on gcc112 shows a couple of signed integer overflows:

config/rs6000/constraints.md:143:33: runtime error: signed integer overflow: 9223372036854775807 + 32768 cannot be represented in type 'long int'
config/rs6000/predicates.md:396:22: runtime error: signed integer overflow: 9223372036854775807 + 2147516416 cannot be represented in type 'long int'
config/rs6000/predicates.md:856:11: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:862:12: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:865:11: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:868:12: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:914:11: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:917:12: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:940:11: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:946:12: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:949:11: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself
config/rs6000/predicates.md:955:12: runtime error: negation of -9223372036854775808 cannot be represented in type 'long int'; cast to an unsigned type to negate this value to itself

2014-11-19  Markus Trippelsdorf  <markus@trippelsdorf.de>

	* config/rs6000/constraints.md: Avoid signed integer overflows.
	* config/rs6000/predicates.md: Likewise.

From-SVN: r217785