Fix 8167 (identity constructor) and 9061 (bitwise ops)
Removed unnecessary allocation and computation
Fixed compilation errors on 64-bit platforms (hopefully)
Merge branch 'master' of https://github.com/D-Programming-Language/phobos

Conflicts:
	std/bigint.d
Got rid of expensive AddOrSubInt call (and related allocation).
Added description of logical (bitwise) operations.
Removed unnecessary allocations in twosComplement call.
Fix name of bitwise operations
Merge pull request #1721 from Biotronic/master

Fix 8167 (BigInt identity constructor) and 9061 (BigInt bitwise ops)