Handle multiline macro definitions

Compress them onto one line for printing in the generated table.

(cherry picked from commit 760155906bc47163bac1fb5622034a9d53e15294)

https://github.com/krb5/krb5/commit/3589b1109ea69fabbf52ceab52253794e6f0ec5c
Author: Ben Kaduk <kaduk@mit.edu>
Committer: Tom Yu <tlyu@mit.edu>
Commit: 3589b1109ea69fabbf52ceab52253794e6f0ec5c
Branch: krb5-1.11
 doc/tools/doxybuilder_types.py |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)