Move assert.h functions into their directory.

libc/Makefile

@@ -17,7 +17,7 @@ CXXFLAGS=-std=gnu++11 -fno-exceptions -fno-rtti
 ASFLAGS=
 
 FREEOBJS=\
-_assert.o \
+assert/_assert.o \
 clearerr.o \
 c++.o \
 ctype.o \

libc/assert/_assert.cpp

@@ -17,7 +17,7 @@
     You should have received a copy of the GNU Lesser General Public License
     along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
 
-    _assert.cpp
+    assert/_assert.cpp
     Reports the occurence of an assertion failure.
 
 *******************************************************************************/