1. Move exepath_*() related code to libc/misc
1. Rename exepath_ to envpath_
2. Rename BINFMT_EXEPATH to LIB_ENVPATH
libs/libc/modlib: Add pre module library symbol table support
configs/olimex-stm32-p407: Various changes as necessary to get the new kelf configuration working.
configs/olimex-stm32-p407: Add kernel ELF (kelf) configuration.