Resolve conflicts for functions introduced in Android API level 18. * m4/getdelim.m4 (gl_FUNC_GETDELIM): Conditionally set REPLACE_GETDELIM. * m4/getline.m4 (gl_FUNC_GETLINE): Conditionally set REPLACE_GETLINE. * lib/stdio.in.h (getdelim, getline): Disable _GL_CXXALIASWARN invocation on non-glibc systems.