main/libxml2: fix pthreads patch for non-musl

the weak hack is needed if -lpthreads is separate library.
so just differentiate with musl and non-musl with __GLIBC__
as an ugly hack.

main/libxml2/APKBUILD

@@ -66,8 +66,8 @@ utils() {
 }
 
 md5sums="9c0cfef285d5c4a5c80d00904ddab380  libxml2-2.9.1.tar.gz
-f5fe0da88617b8d87977640a009b8ea9  libxml2-pthread.patch"
+cc0da520c5296e87407d24166480da73  libxml2-pthread.patch"
 sha256sums="fd3c64cb66f2c4ea27e934d275904d92cec494a8e8405613780cbc8a71680fdb  libxml2-2.9.1.tar.gz
-59e0013398c959df25cf7406e43ad15cccc9bdcfefb6875260bf0daf67c76543  libxml2-pthread.patch"
+97d5e152580774483c47b28483282a4180c2c375bb7716a807ec859e59c3ec2f  libxml2-pthread.patch"
 sha512sums="7b10de749485bc2eb2108063e97d89e70d6fbb78b1bf195ab5528c8c64e79483d55223a49d95934f4e00b00e906c18bdd34344703ffe158dcf08096905a44c1b  libxml2-2.9.1.tar.gz
-1a1c747bfd5f8692ef5df2510dea5572aaf153b597463da0dfd817e53a5cd5c8ebb7e9be88ab787194ccedbf4f2739ada45acf655d38fb40a384004e91062322  libxml2-pthread.patch"
+bda49c5e09605acc2bb36203521f750903d81345cc38af54b977e3ce71e288267fb3ab98f1813d846ab45461490482337f7af8b0f1a8a5e0b2c09e03bbadc7f7  libxml2-pthread.patch"

main/libxml2/libxml2-pthread.patch

---- libxml2-2.9.1.patched/threads.c	2013-07-24 03:30:55.160000003 +0000
-+++ libxml2-2.9.1/threads.c	2013-07-24 03:33:50.323000003 +0000
-@@ -47,49 +47,7 @@
+--- libxml2-2.9.1/threads.c.orig
++++ libxml2-2.9.1/threads.c
+@@ -47,7 +47,7 @@
  #ifdef HAVE_PTHREAD_H
  
  static int libxml_is_threaded = -1;
 -#ifdef __GNUC__
--#ifdef linux
--#if (__GNUC__ == 3 && __GNUC_MINOR__ >= 3) || (__GNUC__ > 3)
--extern int pthread_once (pthread_once_t *__once_control,
--                         void (*__init_routine) (void))
--	   __attribute((weak));
--extern void *pthread_getspecific (pthread_key_t __key)
--	   __attribute((weak));
--extern int pthread_setspecific (pthread_key_t __key,
--                                __const void *__pointer)
--	   __attribute((weak));
--extern int pthread_key_create (pthread_key_t *__key,
--                               void (*__destr_function) (void *))
--	   __attribute((weak));
--extern int pthread_key_delete (pthread_key_t __key)
--	   __attribute((weak));
--extern int pthread_mutex_init ()
--	   __attribute((weak));
--extern int pthread_mutex_destroy ()
--	   __attribute((weak));
--extern int pthread_mutex_lock ()
--	   __attribute((weak));
--extern int pthread_mutex_unlock ()
--	   __attribute((weak));
--extern int pthread_cond_init ()
--	   __attribute((weak));
--extern int pthread_cond_destroy ()
--	   __attribute((weak));
--extern int pthread_cond_wait ()
--	   __attribute((weak));
--extern int pthread_equal ()
--	   __attribute((weak));
--extern pthread_t pthread_self ()
--	   __attribute((weak));
--extern int pthread_key_create ()
--	   __attribute((weak));
--extern int pthread_key_delete ()
--	   __attribute((weak));
--extern int pthread_cond_signal ()
--	   __attribute((weak));
--#endif
--#endif /* linux */
--#endif /* __GNUC__ */
-+
- #endif /* HAVE_PTHREAD_H */
- 
- /*
++#if defined(__GNUC__) && defined(__GLIBC__)
+ #ifdef linux
+ #if (__GNUC__ == 3 && __GNUC_MINOR__ >= 3) || (__GNUC__ > 3)
+ extern int pthread_once (pthread_once_t *__once_control,