Remove -lrt from LDFLAGS.

- This might be required on some embedded system, but from what I can see
  all the functions we use from real time extensions are included in libc
  and the program seems to work fine without it.
- It doesn't exist on MingwW or Mac, so I think it's better to remove it
  completely and add it later on any system that actually requires it.
- Related to #85.

src/Makefile

@@ -64,8 +64,8 @@ INCLUDEDIRS = -I. -I./strategies -I./extras
 
 CC = gcc
 CCFLAGS = $(DFLAGS) -std=gnu99 $(INCLUDEDIRS) $(WARNINGS)
-LDFLAGS += -lm
-LD = gcc -pthread -lrt
+LDFLAGS += -lm -pthread
+LD = gcc
 OBJS = interface_main.o \
   encmain.o \
   bitstream.o \