quote consistently and make tests pass with new quoting from gnulib

Updating to gnulib pulled in new quote and quotarg modules,
by which quoting is now done like 'this' rather than `this'.
That change induces many "make check" test failures.  This change
adapts code and tests so that "make check" passes once again.
* src/scan-code.l: Quote like 'this', not like `this'.
* src/scan-gram.l: Likewise.
* src/symtab.c: Likewise.
* tests/actions.at: Adjust tests to match.
* tests/input.at: Likewise.
* tests/named-refs.at: Likewise.
* tests/output.at: Likewise.
* tests/regression.at: Likewise.
* lib/.gitignore: Regenerate.
* m4/.gitignore: Likewise.

lib/.gitignore

@@ -243,3 +243,19 @@
 /xstrndup.c
 /xstrndup.h
 
+/c-strcaseeq.h
+/fd-hook.c
+/fd-hook.h
+/float.c
+/fstat.c
+/itold.c
+/msvc-inval.c
+/msvc-inval.h
+/msvc-nothrow.c
+/msvc-nothrow.h
+/pathmax.h
+/raise.c
+/strerror-override.c
+/strerror-override.h
+/strerror_r.c
+/xalloc-oversized.h