[libxml2] Revert "Compile testapi with -Wno-unused-function"

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 861823902b780a36d2583c0b742a19b3da3ddd1e
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Mon Nov 13 22:17:53 2017 +0100

    Revert "Compile testapi with -Wno-unused-function"
    
    This reverts commit f404c4f500a0ec18b04463581d5d1b3aae7f7730.
    
    The change broke non-GCC compilers.

 Makefile.am |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)
---
diff --git a/Makefile.am b/Makefile.am
index 15f78e1..748dfc2 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -191,7 +191,6 @@ testapi_SOURCES=testapi.c
 testapi_LDFLAGS = 
 testapi_DEPENDENCIES = $(DEPS)
 testapi_LDADD= $(LDADDS)
-testapi_CFLAGS = -Wno-unused-function
 
 runxmlconf_SOURCES=runxmlconf.c
 runxmlconf_LDFLAGS =