ext2spice/ext2spice.c: Lookup() constify call-site
ext2sim/ext2sim.c: Lookup() constify call-site
windows/windCmdAM.c: Lookup() constify call-site
Tcl_SetResult() uses cast to remove 'const' from type, the pointer
is only used to take a copy of the data, the lack of 'const' is due
to Tcl heritage when supporting C89 era compilers.
TCL9 appears to fix this, in that the macro used ends up at
Tcl_NewStringObj() which has 'const' here.