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/zz40-xc-ovr.m4

@@ -663,4 +663,3 @@ dnl
 m4_pattern_forbid([^_*XC])dnl
 m4_define([$0],[])dnl
 ])
-