.gitattributes: force shell scripts to LF

Bash on Linux errors out on CR characters.
This makes tests 1221 and 1222 pass on Linux with a CRLF checkout.

Ref: https://github.com/curl/curl/pull/1344#issuecomment-289243166
Closes https://github.com/curl/curl/pull/1422

.gitattributes

@@ -4,3 +4,4 @@ configure.ac eol=lf
 *.m4 eol=lf
 *.in eol=lf
 *.am eol=lf
+*.sh eol=lf

lib/.gitattributes

@@ -0,0 +1 @@
+objnames.inc eol=lf