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.

14 files changed, 24 insertions, 15 deletions

diff --git a/include/sys/ipc.h b/include/sys/ipc.h
index 8e2f7172..3f896b8c 100644
--- a/include/sys/ipc.h
+++ b/include/sys/ipc.h
@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_uid_t
 #define __NEED_gid_t
 #define __NEED_mode_t
diff --git a/include/sys/mman.h b/include/sys/mman.h
index 5cfafbed..0fa32e6a 100644
--- a/include/sys/mman.h
+++ b/include/sys/mman.h
@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_mode_t
 #define __NEED_size_t
 #define __NEED_off_t
diff --git a/include/sys/resource.h b/include/sys/resource.h
index bf59d1c8..9536ba35 100644
--- a/include/sys/resource.h
+++ b/include/sys/resource.h
@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_id_t
 #define __NEED_time_t
 #define __NEED_struct_timeval
diff --git a/include/sys/sem.h b/include/sys/sem.h
index add3f1c8..cc3a3e63 100644
--- a/include/sys/sem.h
+++ b/include/sys/sem.h
@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_size_t
 #define __NEED_pid_t
 #define __NEED_time_t
diff --git a/include/sys/sendfile.h b/include/sys/sendfile.h
index 1f2b5231..e7570d8e 100644
--- a/include/sys/sendfile.h
+++ b/include/sys/sendfile.h
@@ -5,6 +5,7 @@
 extern "C" {
 #endif
 
+#include <features.h>
 #include <unistd.h>
 
 ssize_t sendfile(int, int, off_t *, size_t);
diff --git a/include/sys/shm.h b/include/sys/shm.h
index 34117cc8..ce3029f5 100644
--- a/include/sys/shm.h
+++ b/include/sys/shm.h
@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_time_t
 #define __NEED_size_t
 #define __NEED_pid_t
diff --git a/include/sys/stat.h b/include/sys/stat.h
index e16a9682..c63c6b8b 100644
--- a/include/sys/stat.h
+++ b/include/sys/stat.h
@@ -4,11 +4,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_dev_t
 #define __NEED_ino_t
diff --git a/include/sys/statfs.h b/include/sys/statfs.h
index a5a4db9c..d8128a25 100644
--- a/include/sys/statfs.h
+++ b/include/sys/statfs.h
@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #include <sys/statvfs.h>
 
 typedef struct {
diff --git a/include/sys/statvfs.h b/include/sys/statvfs.h
index be41c287..e0839eca 100644
--- a/include/sys/statvfs.h
+++ b/include/sys/statvfs.h
@@ -5,11 +5,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #define __NEED_fsblkcnt_t
 #define __NEED_fsfilcnt_t
diff --git a/include/sys/time.h b/include/sys/time.h
index bf026432..a0ed8e0f 100644
--- a/include/sys/time.h
+++ b/include/sys/time.h
@@ -4,11 +4,7 @@
 extern "C" {
 #endif
 
-#if __STDC_VERSION__ >= 199901L
-#define __restrict restrict
-#elif !defined(__GNUC__)
-#define __restrict
-#endif
+#include <features.h>
 
 #include <sys/select.h>
 
diff --git a/include/sys/types.h b/include/sys/types.h
index f5b64879..7378b60b 100644
--- a/include/sys/types.h
+++ b/include/sys/types.h
@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_ino_t
 #define __NEED_dev_t
 #define __NEED_uid_t
diff --git a/include/sys/uio.h b/include/sys/uio.h
index 7a75a542..624ff422 100644
--- a/include/sys/uio.h
+++ b/include/sys/uio.h
@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #define __NEED_size_t
 #define __NEED_ssize_t
 #define __NEED_struct_iovec
diff --git a/include/sys/utsname.h b/include/sys/utsname.h
index 4c36960f..6b9ea970 100644
--- a/include/sys/utsname.h
+++ b/include/sys/utsname.h
@@ -5,6 +5,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 struct utsname
 {
 	char sysname[65];
diff --git a/include/sys/wait.h b/include/sys/wait.h
index 5e3012ba..8bcac8a3 100644
--- a/include/sys/wait.h
+++ b/include/sys/wait.h
@@ -4,6 +4,8 @@
 extern "C" {
 #endif
 
+#include <features.h>
+
 #include <signal.h>
 
 #define __NEED_pid_t