Cleanup darwin build system some more.

* Convert fs_darwin.cpp and fs_freebsd.cpp to C.
* Convert extern C calls to __BEGIN_DECLS and __END_DECLS macros
* Link rm_attrs with dynamic libroot

headers/build/host/darwin/dirent.h

@@ -1,16 +1,12 @@
 #ifndef _HAIKU_BUILD_COMPATIBILITY_DARWIN_DIRENT
 #define _HAIKU_BUILD_COMPATIBILITY_DARWIN_DIRENT
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include_next <dirent.h>
 
+__BEGIN_DECLS
+
 DIR* fdopendir(int fd);
 
-#ifdef __cplusplus
-}
-#endif
+__END_DECLS
 
 #endif	// _HAIKU_BUILD_COMPATIBILITY_DARWIN_DIRENT

headers/build/host/darwin/fcntl.h

@@ -1,10 +1,6 @@
 #ifndef _HAIKU_BUILD_COMPATIBILITY_DARWIN_FCNTL
 #define _HAIKU_BUILD_COMPATIBILITY_DARWIN_FCNTL
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include_next <fcntl.h>
 #include <sys/time.h>
 
@@ -24,11 +20,11 @@ extern "C" {
 #define AT_SYMLINK_FOLLOW	0x400	/* linkat() */
 #define AT_REMOVEDIR		0x800	/* unlinkat() */
 
+__BEGIN_DECLS
+
 int unlinkat(int fd, const char *path, int flag);
 int futimesat(int fd, const char *path, const struct timeval times[2]);
 
-#ifdef __cplusplus
-}
-#endif
+__END_DECLS
 
 #endif	// _HAIKU_BUILD_COMPATIBILITY_DARWIN_FCNTL

headers/build/host/darwin/regex.h

@@ -3,14 +3,10 @@
 
 // Include the darwin port of gnuregex
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+__BEGIN_DECLS
 
 #include </opt/local/include/gnuregex.h>
 
-#ifdef __cplusplus
-}
-#endif
+__END_DECLS
 
 #endif	// _HAIKU_BUILD_COMPATIBILITY_DARWIN_REGEX

headers/build/host/darwin/stdio.h

@@ -1,17 +1,13 @@
 #ifndef _HAIKU_BUILD_COMPATIBILITY_DARWIN_STDIO
 #define _HAIKU_BUILD_COMPATIBILITY_DARWIN_STDIO
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include_next <stdio.h>
 
+__BEGIN_DECLS
+
 int renameat(int oldFD, const char* oldPath, int newFD, const char* newPath);
 int symlinkat(const char *oldPath, int fd, const char *newPath);
 
-#ifdef __cplusplus
-}
-#endif
+__END_DECLS
 
 #endif	// _HAIKU_BUILD_COMPATIBILITY_DARWIN_STDIO

headers/build/host/darwin/sys/stat.h

@@ -25,10 +25,14 @@
 #	endif
 #endif
 
+__BEGIN_DECLS
+
 int fchmodat(int fd, const char* path, mode_t mode, int flag);
 int fstatat(int fd, const char *path, struct stat *st, int flag);
 int mkdirat(int fd, const char *path, mode_t mode);
 int mkfifoat(int fd, const char *path, mode_t mode);
 int mknodat(int fd, const char *name, mode_t mode, dev_t dev);
 
+__END_DECLS
+
 #endif	/* _HAIKU_BUILD_COMPATIBILITY_DARWIN_SYS_STAT */

headers/build/host/darwin/unistd.h

@@ -1,20 +1,16 @@
 #ifndef _HAIKU_BUILD_COMPATIBILITY_DARWIN_UNISTD
 #define _HAIKU_BUILD_COMPATIBILITY_DARWIN_UNISTD
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include_next <unistd.h>
 
+__BEGIN_DECLS
+
 int faccessat(int fd, const char* path, int accessMode, int flag);
 int fchownat(int fd, const char* path, uid_t owner, gid_t group, int flag);
 ssize_t readlinkat(int fd, const char *path, char *buffer, size_t bufferSize);
 int linkat(int oldFD, const char *oldPath, int newFD, const char *newPath,
 	int flag);
 
-#ifdef __cplusplus
-}
-#endif
+__END_DECLS
 
 #endif	// _HAIKU_BUILD_COMPATIBILITY_DARWIN_UNISTD