make: strip APPLICATION variable

Trailing white spaces in the application Makefile will cause the build
system to fail otherwise.
Merge pull request #1924 from OlegHahm/strip_application_name

make: strip white space from application name
cpu: added `extern "C"` to headers
[SQUASH ME] fixed merge mistake
[SQUASH ME or REMOVE ME] removed intermediate `etern "C"` for m4
[SQUASH ME] removed unrelated newlines and whitespaces
[SQUASH ME] removed/merged `extern "C"`s
[SQUASH ME] merged extern "C"s and repaired merge destructions
[SQUASH ME] one missed
[SQUASH ME] removed unrelated changes to whitespaces (my editor seems to be smarter than me)
[SQUASH ME] removed unrelated whitespaces (my editor is smarter than me)
[SQUASH ME] unrelated newline
[SQUASH ME] removed double etern "C"