apr: bump to 1.7.0 & sync with master

This is a squash of the following cherry-picked commits:

40a29bf055
40c7e95210
893a804c95
12037b3f29
193c3913b6
430ab5f9b3
0c6d461cc9
86396c6a49

Short summary:

- version is bumped to 1.7.0
- Makefile and patches are updated and cleaned
- adds myself as maintainer
- improves the cross-compile setup (via configure variables, patches &
  sed scripts)

For more details please check the individual commits provided above.

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>

libs/apr/patches/302-add-cache-for-strerror_r.patch

@@ -0,0 +1,30 @@
+--- a/build/apr_common.m4
++++ b/build/apr_common.m4
+@@ -526,8 +526,9 @@ dnl  string.
+ dnl
+ dnl
+ AC_DEFUN([APR_CHECK_STRERROR_R_RC], [
+-AC_MSG_CHECKING(for type of return code from strerror_r)
+-AC_TRY_RUN([
++AC_CACHE_CHECK([whether return code from strerror_r has type int],
++[ac_cv_strerror_r_rc_int],
++[AC_TRY_RUN([
+ #include <errno.h>
+ #include <string.h>
+ #include <stdio.h>
+@@ -543,14 +544,10 @@ main()
+ }], [
+     ac_cv_strerror_r_rc_int=yes ], [
+     ac_cv_strerror_r_rc_int=no ], [
+-    ac_cv_strerror_r_rc_int=no ] )
++    ac_cv_strerror_r_rc_int=no ] ) ] )
+ if test "x$ac_cv_strerror_r_rc_int" = xyes; then
+   AC_DEFINE(STRERROR_R_RC_INT, 1, [Define if strerror returns int])
+-  msg="int"
+-else
+-  msg="pointer"
+ fi
+-AC_MSG_RESULT([$msg])
+ ] )
+ 
+ dnl