title: problem with libnet install
body: <p>when i install libnet by sudo apt-get install libnet1, the program can not find libnet.h and I also can not find it at /usr/local/include or /usr/include.
  so i download the libnet and make it, but I get the errors</p>
  
  <pre><code>make -C lib/ lib
  make[1]: Entering director `/home/liuqiang/workspace/libnet/lib'
  gcc -O2 -Wall -Werror -Wno-unused -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -g -I../include -Iinclude -DTARGET_LINUX   -c -o core/config.o core/config.c
  cc1: warnings being treated as errors
  core/config.c: In function ‘__libnet_internal__seek_section’:
  core/config.c:87: error: ignoring return value of ‘fgets’, declared with attribute warn_unused_result
  core/config.c: In function ‘__libnet_internal__get_setting’:
  core/config.c:111: error: ignoring return value of ‘fgets’, declared with attribute warn_unused_result
  make[1]: *** [core/config.o] error 1
  make[1]:Leaving directory `/home/liuqiang/workspace/libnet/lib'
  make: *** [lib] error 2
  </code></pre>