Fix build error when building a shared libunistring on Android. * tests/uninorm/test-nfc.c (n): Don't define on Android. (main): Add 'volatile', to defeat a GCC optimization that would eliminate the reference. * tests/uninorm/test-nfd.c (n): Don't define on Android. (main): Add 'volatile', to defeat a GCC optimization that would eliminate the reference. * tests/uninorm/test-nfkc.c (n): Don't define on Android. (main): Add 'volatile', to defeat a GCC optimization that would eliminate the reference. * tests/uninorm/test-nfkd.c (n): Don't define on Android. (main): Add 'volatile', to defeat a GCC optimization that would eliminate the reference.

Files:
tests/test-strstr.c
tests/zerosize-ptr.h
tests/signature.h
tests/macros.h
m4/mmap-anon.m4

Depends-on:
extensions
getpagesize

configure.ac:
AC_CHECK_DECLS_ONCE([alarm])
gl_FUNC_MMAP_ANON
AC_CHECK_HEADERS_ONCE([sys/mman.h])
AC_CHECK_FUNCS_ONCE([mprotect])

Makefile.am:
TESTS += test-strstr
check_PROGRAMS += test-strstr