Remove some unused Makefile.in variables.

Remove some unused Makefile.in variables.

* configure.in (AC_PROG_LN_S): Remove test, nothing uses @LN_S@.

* Makefile.in (CPP, C_SWITCH_SYSTEM, ALLOCA, LN_S, C_SWITCH_X_SITE)
(LD_SWITCH_X_SITE): Remove unused variables.

* lwlib/Makefile.in (CPP, LN_S, TOP, LN): Remove unused variables.

* oldXMenu/Makefile.in (CPP, LN_S, AS, LD, MV, LS, LINTOPTS, LINTLIBFLAG, MAKE)
(STD_DEFINES, CDEBUGFLAGS, RM_CMD): Remove unused variables.

* src/Makefile.in (CPP, LN_S): Remove unused variables.

* msdos/sed1v2.inp, msdos/sed5x.inp: Remove LN_S, unused.