Added library_subdir hook variable + fixed use of MAPTK_LIB_SUFFIX
Added library_subdir hook variable + fixed use of MAPTK_LIB_SUFFIX

Library suffix string should only affect the location the libraries are
insatlled to, not the locations where build products are placed.

linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk,linus-sherrill/maptk