whitespace fixes

- replace tabs with spaces where possible
- remove line ending spaces
- remove double/triple newlines at EOF
- fix a non-UTF-8 character
- cleanup a few indentations/line continuations
  in manual examples

Closes https://github.com/curl/curl/pull/3037

m4/curl-reentrant.m4

@@ -614,4 +614,3 @@ AC_DEFUN([CURL_CONFIGURE_THREAD_SAFE], [
   fi
   #
 ])
-