Expand comments in elf/ldconfig.c (search_dir)

Developers creating development packages must take care
to have their static linker DSO link point to the actual
SONAME file. This allows ldconfig to correctly create
the required links for the SONAME. The behaviour is now
more clearly documented in a code comment added by this
patch.
Use ALIGN_UP in nptl/nptl-init.c

Replace bespoke code to align a value with
the ALIGN_UP macro to make it easier to read.
Fix indenting in bits/ioctl-types.h.

Indent the preprocessor directives correctly according
to the normal glibc style.