* Makefile.am: Set environment variables for tests.
* configure.ac: Add language support for Objective-C and Objective-C++.
* build-aux/ltmain.in: Update help message for tags available.
* m4/libtool.m4: Add tagging support for OBJC and OBJCXX.
* tests/flags.at: Add tests for passing OBJC and OBJCXX flags.
* tests/infer-tag.at: Add tests for inferring OBJC and OBJCXX tags.
* doc/libtool.texi: Update documentation.
* NEWS: Update.