Check return values of read() and write().  Avoid some unsigned
comparisons.  Cast a ptrdiff_t value to int for use with %d in a
format string.

[ghudson@mit.edu: rewrap long lines; fix one more warning; commit
message]

In a static build, linking dbtest could fail on platforms where libdb2
depends on krb5support (platforms without a native mkstemp).  Reported
by Gilles Espinasse <g.esp@free.fr>.

ticket: 7651

Provide default values in pre.in for PROG_LIBPATH, PROG_RPATH,
SHLIB_DIRS, SHLIB_RDIRS, and STOBJLISTS so that they don't have to be
specified in the common case.  Rename KRB5_RUN_ENV and KRB5_RUN_VARS
to RUN_SETUP (already the most commonly used name) and RUN_VARS.  Make
sure to use DEFINES for local defines (not DEFS).  Remove some other
unnecessary makefile content.

Locking and unlocking a non-recursive mutex is a simple memory
operation and should not fail on any reasonable platform with correct
usage.  A pthread mutex can return EDEADLK on lock or EPERM on unlock,
or EINVAL if the mutex is uninitialized, but all of these conditions
would reflect serious bugs in the calling code.

Change the k5_mutex_lock and k5_mutex_unlock wrappers to return void
and adjust all call sites.  Propagate this change through
k5_cc_mutex_lock and k5_cc_mutex_unlock as well.

The locking wrapper for audit_as_req used the wrong function
signature, which was harmless but produced a couple of warnings.  Fix
it.

For easier static analysis, make sure that krb5_decode_princ_entry
always sets *entry_ptr to a valid entry or NULL.

ticket: 7585

Add k5-int.h static functions to duplicate byte ranges, optionally
with a trailing zero byte, and set an error code like k5alloc does.
Use them where they would shorten existing code.

Mostly this gets rid of the trailing space on line 2 after
bb76891f5386526bdf91bc790c614fc9296cb5fa.