[newlib-cygwin] Fix pdf build failure with texinfo 6.1.0

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=cf6e411f17be3bdce2df24911517798df4172859

commit cf6e411f17be3bdce2df24911517798df4172859
Author: Thomas Preudhomme <thomas.preudhomme@foss.arm.com>
Date:   Tue Oct 25 16:11:09 2016 +0100

    Fix pdf build failure with texinfo 6.1.0
    
    Hi,
    
    make pdf on Ubuntu 16.04 fail with:
    
    newlib/libc/libc.texinfo:9: Missing @endcsname inserted.
    
    After a lot of fiddling the reason appears to be the combination of concept
    and function index despite a lack of concept index entries. Arguably texinfo
    should not error in that case but here we are, newlib will fail to build its
    documentation on some systems because of this. Since libc.texinfo only
    contains function index entries this patch simply removes the combination of
    indices. It does the same for libm.texinfo which has concept index entries but
    no function index entries.
    
    Tested by running make pdf, make dvi, make info and make html successfully.
    libc.pdf appears to have only one index as expected.
    
    == Proposed commit message ==
    
    Fix pdf build failure with texinfo 6.1.0 as provided in Ubuntu 16.04. Index
    combination in libc.texinfo and libm.texinfo fails because both file have only
    one type of index entries. Removing index combination is thus harmless and
    solves the problem.
    
    Is this ok for master?
    
    Best regards,
    
    Thomas

Diff:
---
 newlib/libc/libc.texinfo | 1 -
 newlib/libm/libm.texinfo | 1 -
 2 files changed, 2 deletions(-)

diff --git a/newlib/libc/libc.texinfo b/newlib/libc/libc.texinfo
index 6216c99..482b0ed 100644
--- a/newlib/libc/libc.texinfo
+++ b/newlib/libc/libc.texinfo
@@ -1,6 +1,5 @@
 \input texinfo.tex
 @setfilename libc.info
-@syncodeindex fn cp
 
 @ifinfo
 @format
diff --git a/newlib/libm/libm.texinfo b/newlib/libm/libm.texinfo
index 5c28975..1b5be1f 100644
--- a/newlib/libm/libm.texinfo
+++ b/newlib/libm/libm.texinfo
@@ -1,6 +1,5 @@
 \input texinfo.tex
 @setfilename libm.info
-@syncodeindex fn cp
 
 @ifinfo
 @format