statvfs: use libssh2_sftp_statvfs only, no "_ex"

As the long-term goal is to get rid of the extensive set of
macros from the API we can just as well start small by not adding
new macros when we add new functions. Therefore we let the
function be libssh2_sftp_statvfs() plainly without using an _ex
suffix.

I also made it use size_t instead of unsigned int for the string
length as that too is a long-term goal for the API.

docs/Makefile.am

@@ -138,7 +138,6 @@ dist_man_MANS = \
 	libssh2_sftp_stat.3 \
 	libssh2_sftp_stat_ex.3 \
 	libssh2_sftp_statvfs.3 \
-	libssh2_sftp_statvfs_ex.3 \
 	libssh2_sftp_symlink.3 \
 	libssh2_sftp_symlink_ex.3 \
 	libssh2_sftp_tell.3 \

docs/libssh2_sftp_statvfs.3

@@ -7,10 +7,8 @@ libssh2_sftp_statvfs, libssh2_sftp_fstatvfs - get file system statistics
 #include <libssh2_sftp.h>
 
 int
-libssh2_sftp_statvfs_ex(LIBSSH2_SFTP *sftp, const char *path,
-                        unsigned int path_len, LIBSSH2_SFTP_STATVFS *st);
-#define libssh2_sftp_statvfs(sftp, path, st) \\
-    libssh2_sftp_statvfs_ex((sftp), (path), strlen(path), (st))
+libssh2_sftp_statvfs(LIBSSH2_SFTP *sftp, const char *path,
+                     size_t path_len, LIBSSH2_SFTP_STATVFS *st);
 
 int
 libssh2_sftp_fstatvfs(LIBSSH2_SFTP_HANDLE *handle,

docs/libssh2_sftp_statvfs_ex.3

@@ -1 +0,0 @@
-.so man3/libssh2_sftp_statvfs.3