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
sched/: Convert legitimate uses of task_create() to nxtask_create(). Review handling of returned values from all uses of kthread_create() (as well as nxtask_create()).
graphics/: Review return values for all calls to kthread_start() because it no longer returns an errno.
drivers/: threads started by drivers should be kernel threads, not user tasks. Review return values for all calls to kthread_start() because it no longer returns an errno.
configs/: threads started by board bringup logic should be kernel threads, not user tasksi (part 2 of 2).
sched/task: Add nxtask_create(). Kthread_create() and nxtask_create() are internal OS functions and should not modify the errno variable. configs/: threads started by board bringup logic should be kernel threads, not user tasks.
sched/sched: Correct some build issues introduced by last set of changes.
sched/sched: Add new internal OS function nxsched_setaffinity() that is identical to sched_isetaffinity() except that it does not modify the errno value. All usage of sched_setaffinity() within the OS is replaced with nxsched_setaffinity().
sched/sched: Internal functions sched_reprioritize() and sched_setpriority() no longer movidify the errno value. Also renamed to nxsched_reprioritize() and sched_setpriority().
sched/sched: Add new internal OS function nxsched_getscheduler() that is identical to sched_getscheduler() except that it does not modify the errno value. All usage of sched_getscheduler() within the OS is replaced with nxsched_getscheduler().
sched/sched: Add new internal OS function nxsched_setparam() that is identical to sched_setparam() except that it does not modify the errno value. All usage of sched_setparam() within the OS is replaced with nxsched_setparam().
sched/sched: Add new internal OS function nxsched_getparam() that is identical to sched_getparam() except that it does not modify the errno value (actually, the previous value erroneously neglected to set the errno value to begin with, but this fixes both issues). All usage of sched_getparam() within the OS is replaced with nxsched_getparam().
