Include iLBC source code for distribution with Asterisk

This patch includes the iLBC source code for distribution with Asterisk.
Clarification regarding the iLBC source code was provided by Google, and
the appropriate licenses have been included in the codecs/ilbc folder.

Review: https://reviewboard.asterisk.org/r/1675
Review: https://reviewboard.asterisk.org/r/1649

(closes issue: ASTERISK-18943)
Reporter: Leif Madsen
Tested by: Matt Jordan
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Merged revisions 351450 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 351451 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@351452 65c4cc65-6c06-0410-ace0-fbb531ad65f3

codecs/ilbc/LPCdecode.h

@@ -0,0 +1,52 @@
+
+   /******************************************************************
+
+       iLBC Speech Coder ANSI-C Source Code
+
+       LPC_decode.h
+
+       Copyright (C) The Internet Society (2004).
+       All Rights Reserved.
+
+   ******************************************************************/
+
+   #ifndef __iLBC_LPC_DECODE_H
+   #define __iLBC_LPC_DECODE_H
+
+   void LSFinterpolate2a_dec(
+       float *a,           /* (o) lpc coefficients for a sub-frame */
+       float *lsf1,    /* (i) first lsf coefficient vector */
+       float *lsf2,    /* (i) second lsf coefficient vector */
+       float coef,         /* (i) interpolation weight */
+       int length          /* (i) length of lsf vectors */
+   );
+
+   void SimplelsfDEQ(
+       float *lsfdeq,      /* (o) dequantized lsf coefficients */
+       int *index,         /* (i) quantization index */
+       int lpc_n           /* (i) number of LPCs */
+   );
+
+   void DecoderInterpolateLSF(
+       float *syntdenum,   /* (o) synthesis filter coefficients */
+       float *weightdenum, /* (o) weighting denumerator
+                                  coefficients */
+       float *lsfdeq,      /* (i) dequantized lsf coefficients */
+       int length,         /* (i) length of lsf coefficient vector */
+       iLBC_Dec_Inst_t *iLBCdec_inst
+                           /* (i) the decoder state structure */
+   );
+
+   #endif
+
+
+
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+