build: remove checks introduced by autoscan.

Therre is no current use of HAVE_* variables for these checks in the
code, so there is no reason to keep the checks around.

Signed-off-by: Diego Elio Pettenò <flameeyes@flameeyes.eu>
diff --git a/configure.ac b/configure.ac
index 101a1e8..fdaf15a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,10 +15,6 @@
 
 AC_CONFIG_MACRO_DIR([m4])
 
-dnl checks for header files
-AC_HEADER_STDC
-AC_CHECK_HEADERS(execinfo.h sys/select.h sys/socket.h syslog.h ctype.h)
-
 # The following test is taken from WebKit's webkit.m4
 saved_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS -fvisibility=hidden "