fix issues with pthread and dlsym symbols on ubuntu 12.04

for some reason, the linker needs --no-as-needed for both
libdl and libpthread.

closes #4

thanks to @tomsawyer for discovering this.

the proposed -pthread change was not needed though,
and this is a good thing since it seems not portable.

Makefile

@@ -18,7 +18,7 @@ OBJS = $(SRCS:.c=.o)
 LOBJS = src/core.o src/common.o src/libproxychains.o
 
 CFLAGS  += -Wall -O0 -g -std=c99 -D_GNU_SOURCE -pipe -DTHREAD_SAFE
-LDFLAGS = -shared -fPIC -ldl -lpthread
+LDFLAGS = -shared -fPIC -Wl,--no-as-needed -ldl -lpthread
 INC     = 
 PIC     = -fPIC
 AR      = $(CROSS_COMPILE)ar