Update Android port

Update Android port

* .gitignore: Ignore lib/math.h.
* INSTALL.android: Update accordingly.
* build-aux/ndk-build-helper-1.mk:
* build-aux/ndk-build-helper-2.mk:
* build-aux/ndk-build-helper.mk:
* build-aux/ndk-module-extract.awk: Handle C++ modules.
* configure.ac: Enable libxml2 on Android.

* cross/ndk-build/Makefile.in:
* cross/ndk-build/ndk-build-shared-library.mk:
* cross/ndk-build/ndk-build-static-library.mk:
* cross/ndk-build/ndk-build.mk.in:
* cross/ndk-build/ndk-resolve.mk: Fix dependency resolution of
includes.

* java/org/gnu/emacs/EmacsView.java (popupMenu): Fix minimum SDK
version for actual popup menus.
* lib/math.h: Delete file.

* m4/ndk-build.m4 (ndk_SEARCH_MODULE, ndk_CHECK_MODULES): Look
for nasm and C++ libraries.

* src/android.c (faccessat): Rename to `android_faccessat'.
* src/android.h: Update prototypes.
* src/dired.c (file_name_completion_dirp):
* src/fileio.c (file_access_p, Faccess_file, file_directory_p):
* src/lisp.h:
* src/lread.c (openp):
* src/process.c (allocate_pty): Use sys_faccessat.
* src/sysdep.c (sys_faccessat): New function.