'RELENG_3_3_0_RELEASE'.

This commit was manufactured to restore the state of the 3.3-RELEASE image.
Releases prior to 5.3-RELEASE are omitting the secure/ and crypto/ subdirs.

substitution errors for variables that don't exist.

If a machine architecture dependent makefile exists, include it
to discover if libc or libc_r is being built with NetBSD syscalls
instead of FreeBSD ones.

Put a NO_QUAD thingy around the quad makefile so that 64-bit
architectures can ignore that sh*t.

In the test for MDSRCS being empty, add all MISRCS to SRCS, rather
than just ignoring them.

The names of m-d variants are now added (manually) to MDSRCS instead
of to SRCS, and the names of all machine-independent (m-i) variants
that can reasonably be replaced by an m-d variant are now added
(manually) to MISRCS instead of to SRCS, so that a simple substitution
can be used to discard the unused m-i variants.  MISRCS is potentially
all m-i sources, but the substitution is too simple to be fast, so
MISRCS should be kept reasonably small.

libc/Makefile.inc:
Do the substitution.

libc/i386/string/Makefile.inc:
Add to MDSRCS instead of to SRCS.  Add the names of all sources in this
directory, but no others.

libc/string/Makefile.inc
Add to MISRCS instead of to SRCS.  Add the names of all sources in this
directory.  Don't use (broken) explicit rules for special cases.

so that all these makefiles can be used to build libc_r too.

Added .if ${LIB} == "c" tests to restrict man page builds to libc
to avoid needlessly building them with libc_r too.

Split libc Makefile into Makefile and Makefile.inc to allow the
libc_r Makefile to include Makefile.inc too.