Recommit: Stop intercepting some malloc-related functions on FreeBSD
and macOS

Summary:
In https://bugs.freebsd.org/215125 I was notified that some configure
scripts attempt to test for the Linux-specific `mallinfo` and
`mallopt` functions by compiling and linking small programs which
references the functions, and observing whether that results in
errors.

FreeBSD and macOS do not have the `mallinfo` and `mallopt` functions,
so normally these tests would fail, but when sanitizers are enabled,
they incorrectly succeed, because the sanitizers define interceptors
for these functions.  This also applies to some other malloc-related
functions, such as `memalign`, `pvalloc` and `cfree`.

Fix this by not intercepting `mallinfo`, `mallopt`, `memalign`,
`pvalloc` and `cfree` for FreeBSD and macOS, in all sanitizers.

Also delete the non-functional `cfree` wrapper for Windows, to fix the
test cases on that platform.

Reviewers: emaste, kcc, rnk

Subscribers: timurrrr, eugenis, hans, joerg, llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D27654