Cherry-pick [http://core.tcl.tk/tcl/info/a37bbd81ea20b5c8be680b847b91fa920bfc060b|a37bbd81ea] from Tcl, for use in TEA as well: Combine TCL_SHLIB_LD_EXTRAS+TK_SHLIB_LD_EXTRAS (for Cygwin and FreeBSD) to a single SHLIB_LD_LIBS usable for both Tcl and Tk.
Better pic flag for OpenBSD.