[libxml2] threads: use forward declarations only for glibc

[Daniel Veillard <veillard src gnome org>]

commit fff8a6b87e05200a0ad0af6f86c2e859c7de9172
Author: Michael Heimpold <mhei heimpold de>
Date:   Mon Dec 22 11:12:12 2014 +0800

    threads: use forward declarations only for glibc
    
    Fixes bug #704908
    
    The declarations of pthread functions, used to generate weak references
    to them, fail to suppress macros. Thus, if any pthread function has
    been provided as a macro, compiling threads.c will fail.
    This breaks on musl libc, which defines pthread_equal as a macro (in
    addition to providing the function, as required).
    
    Prevent the declarations for e.g. musl libc by refining the condition.
    
    The idea for this solution was borrowed from the alpine linux guys, see
    http://git.alpinelinux.org/cgit/aports/tree/main/libxml2/libxml2-pthread.patch
    
    Signed-off-by: Michael Heimpold <mhei heimpold de>

 threads.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/threads.c b/threads.c
index 8921204..78006a2 100644
--- a/threads.c
+++ b/threads.c
@@ -47,7 +47,7 @@
 #ifdef HAVE_PTHREAD_H
 
 static int libxml_is_threaded = -1;
-#ifdef __GNUC__
+#if defined(__GNUC__) && defined(__GLIBC__)
 #ifdef linux
 #if (__GNUC__ == 3 && __GNUC_MINOR__ >= 3) || (__GNUC__ > 3)
 extern int pthread_once (pthread_once_t *__once_control,
@@ -89,7 +89,7 @@ extern int pthread_cond_signal ()
           __attribute((weak));
 #endif
 #endif /* linux */
-#endif /* __GNUC__ */
+#endif /* defined(__GNUC__) && defined(__GLIBC__) */
 #endif /* HAVE_PTHREAD_H */
 
 /*