add put*ent functions for passwd/group files and similar for shadow since shadow does not yet support enumeration (getspent), the corresponding FILE-based get and put versions are also subbed out for now. this is partly out of laziness and partly because it's not clear how they should work in the presence of TCB shadow files. the stubs should make it possible to compile some software that expects them to exist, but such software still may not work properly.
default features: make musl usable without feature test macros the old behavior of exposing nothing except plain ISO C can be obtained by defining __STRICT_ANSI__ or using a compiler option (such as -std=c99) that predefines it. the new default featureset is POSIX with XSI plus _BSD_SOURCE. any explicit feature test macros will inhibit the default. installation docs have also been updated to reflect this change.
move getpass decl to the right place
add fgetpwent (nonstandard function) based on patch by Jeremy Huntwork
prototype for getpass
initial check-in, version 0.5.0