libexpr: Deprecate CR and CRLF line endings

They are broken beyond repair, and barring a language version revision
this is our only option besides doing nothing about it.

Change-Id: I25fa4f032ca9b5ca67356946bcd889289583592e

tests/functional/lang/eval-okay-unsafeGetAttrPos.flags

@@ -0,0 +1 @@
+--extra-deprecated-features cr-line-endings

tests/functional/lang/parse-fail-crlf.err.exp

@@ -0,0 +1,7 @@
+warning: CR (`\r`) and CRLF (`\r\n`) line endings found at «stdin»:7:21. Please inspect the file and normalize it to use LF (`\n`) line endings instead. Use --extra-deprecated-features cr-line-endings to silence this warning.
+error: CR (`\r`) and CRLF (`\r\n`) line endings are not supported. Please inspect the file and normalize it to use LF (`\n`) line endings instead. Use --extra-deprecated-features cr-line-endings to silence this warning.
+       at «stdin»:14:15:
+           13|   # translated to LF.
+           14|   foo = "multi
+             |               ^
+           15| line

tests/functional/lang/parse-fail-crlf.nix

@@ -0,0 +1 @@
+parse-okay-crlf.nix

tests/functional/lang/parse-fail-eol-2.flags

@@ -0,0 +1 @@
+--extra-deprecated-features cr-line-endings

tests/functional/lang/parse-fail-eol-3.flags

@@ -0,0 +1 @@
+--extra-deprecated-features cr-line-endings

tests/functional/lang/parse-okay-crlf.flags

@@ -0,0 +1 @@
+--extra-deprecated-features cr-line-endings