Makefile.am (install-glibcppinstallHEADERS, [...]): Have explicit rules catering to SUN make VPATH peculiarities.

	* libsupc++/Makefile.am (install-glibcppinstallHEADERS,
	uninstall-glibcppinstallHEADERS): Have explicit rules catering to
	SUN make VPATH peculiarities.
	* libsupc++/Makefile.in: Regenerate.

From-SVN: r42844