[ms] Make mangleIntegerLiteral less aware of exact type of the literal.

Integer literal mangling does not actually depend on exact type of the literal.
This will simplify calling mangleIntegerLiteral when literal type is not known,
for example, when sizes or offsets are mangled as integer literals.

Also, call mangleNumber instead of directly printing mangled values of 0/1, to
avoid this knowledge from being in multiple places.

Patch from Evgeny Eltsin!

llvm-svn: 167878