Add a new LibCallAliasAnalysis pass, which is parameterized

Add a new LibCallAliasAnalysis pass, which is parameterized
by an instance of LibCallInfo to provide mod/ref info of
standard library functions.  This is powerful enough to
say that 'sqrt' is readonly except that it modifies errno,
or that "printf doesn't store to memory unless the %n
constraint is present" etc.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50827 91177308-0d34-0410-b5e6-96231b3b80d8