clang-format: Add new style option AlignConsecutiveMacros
This option behaves similarly to AlignConsecutiveDeclarations and
AlignConsecutiveAssignments, aligning the assignment of C/C++
preprocessor macros on consecutive lines.
I've worked in many projects (embedded, mostly) where header files full
of large, well-aligned "#define" blocks are a common pattern. We
normally avoid using clang-format on these files, since it ruins any
existing alignment in said blocks. This style option will align "simple"
PP macros (no parameters) and PP macros with parameter lists on
Related Bugzilla entry (thanks mcuddie):
Patch by Nick Renieris (VelocityRa)!
Differential Revision: https://reviews.llvm.org/D28462