Fix insignificant CRTP bug

Summary:

@override-unit-failures
Flaky unit tests passed on the second try, but the git hook still
complains

Test Plan: iobuf_cursor_test

Reviewed By: philipp@fb.com

FB internal diff: D948768
x86intrinsic seems to be problematic for clang

Summary: fbinject (clang code parser) throws some errors when
including the x86intrinsic header.

Test Plan:
D929356 compiles after this diff.  It adds a dep on RWSpinLock.

Reviewed By: beng@fb.com

FB internal diff: D950285
abort instead of throwing an exception on bad format strings

Summary:
Errors that happen during format are almost always programmer
error in the form of a bad format string. Abort instead of throwing in
these cases.

Test Plan: automated tests, added a couple new tests

Reviewed By: tudorb@fb.com

FB internal diff: D947470
folly: disable address sanitizer warnings on fbstring

Summary:
The fbstring constructor does word-aligned copies which may creep
past the end of the C string, which address sanitizer doesn't like.

This also adds a address-sanitizer-disabling-attribute to both
Portability.h (for general use) and a (gross) copy in FBString.h
since it gets put into libstdc++.

Test Plan: ran address sanitizer on folly tests

Reviewed By: andrei.alexandrescu@fb.com

FB internal diff: D950586
Some fixes for building stuff with clang

@override-unit-failures

Summary: Not that much.

Test Plan:
Compiled hphp with clang.

Reviewed By: oyamauchi@fb.com

FB internal diff: D954663