These functions are in POSIX; hypot() is in C99. Also build cabs()
because it rides with hypot(), but don't declare cabs() in any header
file, because our compiler can't parse C99 "double complex" type.
Touch build.lua so it sees that .c files moved.
This undoes part of bfeb736, and returns to using DBL_MAX_EXP and
DBL_MIN_EXP from float.h.
Add a dependency on math/localmath.h and other local header files so
libc is rebuilt when those headers change.
These files "magically reappeared" after the conversion from CVS to
Mercurial. The old CVS repository deleted these files but did not
record *when* it deleted these files. The conversion resurrected these
files because they have no history of deletion. These files were
probably deleted before year 1995. The CVS repository begins to record
deletions around 1995.
These files may still appear in older revisions of this Mercurial
repository, when they should already be deleted. There is no way to fix
this, because the CVS repository provides no dates of deletion.
See http://sourceforge.net/mailarchive/message.php?msg_id=29823032
