rename libwebp.i -> libwebp.swig

.swig provides better tool compatibility

Change-Id: I35587b84dd32e12e8cedad14b36ac518b63896bc

README

@@ -80,7 +80,7 @@ more options.
 SWIG bindings:
 --------------
 
-To generate language bindings from swig/libwebp.i at least swig-1.3
+To generate language bindings from swig/libwebp.swig at least swig-1.3
 (http://www.swig.org) is required.
 
 Currently the following functions are mapped:
@@ -115,7 +115,7 @@ DLL that can be loaded via System.loadLibrary("webp_jni").
 Python bindings:
 
 To build the swig-generated Python extension code at least Python 2.6 is
-required. Python < 2.6 may build with some minor changes to libwebp.i or the
+required. Python < 2.6 may build with some minor changes to libwebp.swig or the
 generated code, but is untested.
 
 Encoding tool:

swig/libwebp.swig

@@ -17,12 +17,12 @@
   $ swig -java \
          -package com.google.webp \
          -outdir java/com/google/webp \
-         -o libwebp_java_wrap.c libwebp.i
+         -o libwebp_java_wrap.c libwebp.swig
 
   Python bindings:
   $ swig -python \
          -outdir . \
-         -o libwebp_python_wrap.c libwebp.i
+         -o libwebp_python_wrap.c libwebp.swig
 */
 
 #ifdef SWIGPYTHON