一、下载libcurl http://curl.haxx.se/download/curl-7.21.1.tar.gz
二、安装 指定了安装目录 /usr/local/curl
注意：在这里最好用默认的路径
命令1: ./configure --prefix=/usr/local/curl该为命令：./configure
这样，在编译程序的时候直接使用 gcc -o filename -Wall filename.c -lcurl 就不会出现编译链接错误，
如果你的路径改变了，那么在编译程序时可能会比较麻烦。
结果：
curl version: 7.21.1
Host setup: i686-pc-linux-gnu
Install prefix: /usr/local/curl
Compiler: gcc
SSL support: enabled (OpenSSL)
SSH support: no (--with-libssh2)
zlib support: enabled
krb4 support: no (--with-krb4*)
GSSAPI support: no (--with-gssapi)
SPNEGO support: no (--with-spnego)
resolver: default (--enable-ares / --enable-threaded-resolver)
ipv6 support: enabled
IDN support: enabled
Build libcurl: Shared=yes, Static=yes
Built-in manual: enabled
Verbose errors: enabled (--disable-verbose)
SSPI support: no (--enable-sspi)
ca cert bundle: /etc/ssl/certs/ca-certificates.crt
ca cert path: no
LDAP support: enabled (OpenLDAP)
LDAPS support: enabled
RTSP support: enabled
RTMP support: no (--with-librtmp)
Protocols: DICT FILE FTP FTPS HTTP HTTPS IMAP IMAPS LDAP LDAPS POP3 POP3S RTSP SMTP SMTPS TELNET TFTP
命令2：make
命令3：sudo make install
可以看到lib库，已经安装在 /usr/local/curl/lib
----------------------------------------------------------------------
Libraries have been installed in:
/usr/local/curl/lib
If you ever happen to want to link against installed libraries
in a given directory, LIBDIR, you must either use libtool, and
specify the full pathname of the library, or use the `-LLIBDIR'
flag during linking and do at least one of the following:
- add LIBDIR to the `LD_LIBRARY_PATH' environment variable
during execution
- add LIBDIR to the `LD_RUN_PATH' environment variable
during linking
- use the `-Wl,-rpath -Wl,LIBDIR' linker flag
- have your system administrator add LIBDIR to `/etc/ld.so.conf'
See any operating system documentation about shared libraries for
more information, such as the ld(1) and ld.so(8) manual pages.
在安装目录下/usr/local/curl下会有四个目录 bin include lib share 包含了所需的库、头文件等