Rename some "python3" symbols to "py3", as the command name.
Documentation updates.
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index 3e83ef7..e45796f 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -741,7 +741,7 @@
 			RANGE|EXTRA|NEEDARG|CMDWIN),
 EX(CMD_pyfile,		"pyfile",	ex_pyfile,
 			RANGE|FILE1|NEEDARG|CMDWIN),
-EX(CMD_python3,		"py3",	ex_python3,
+EX(CMD_py3,		"py3",		ex_py3,
 			RANGE|EXTRA|NEEDARG|CMDWIN),
 EX(CMD_py3file,		"py3file",	ex_py3file,
 			RANGE|FILE1|NEEDARG|CMDWIN),
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index c57db94..b56fb67 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -270,7 +270,7 @@
 # define ex_pyfile		ex_ni
 #endif
 #ifndef FEAT_PYTHON3
-# define ex_python3		ex_script_ni
+# define ex_py3			ex_script_ni
 # define ex_py3file		ex_ni
 #endif
 #ifndef FEAT_TCL
@@ -2562,7 +2562,7 @@
 	    case CMD_perl:
 	    case CMD_psearch:
 	    case CMD_python:
-	    case CMD_python3:
+	    case CMD_py3:
 	    case CMD_return:
 	    case CMD_rightbelow:
 	    case CMD_ruby:
@@ -2825,7 +2825,7 @@
     {
 	while (ASCII_ISALPHA(*p))
 	    ++p;
-	/* for python 3.x support (:py3, :python3) */
+	/* for python 3.x support ":py3" (and ":py4" :-) */
 	if (eap->cmd[0] == 'p' && eap->cmd[1] == 'y')
 	    p = skipdigits(p);
 
diff --git a/src/if_python3.c b/src/if_python3.c
index 410dc14..422878a 100644
--- a/src/if_python3.c
+++ b/src/if_python3.c
@@ -630,9 +630,9 @@
 }
 
 /*
- * ":python3"
+ * ":py3"
  */
-void ex_python3(exarg_T *eap)
+void ex_py3(exarg_T *eap)
 {
     char_u *script;
 
diff --git a/src/proto/if_python3.pro b/src/proto/if_python3.pro
index a2c7e4c..f9921e1 100644
--- a/src/proto/if_python3.pro
+++ b/src/proto/if_python3.pro
@@ -1,7 +1,7 @@
 /* if_python3.c */
 int python3_enabled __ARGS((int verbose));
 void python3_end __ARGS((void));
-void ex_python3 __ARGS((exarg_T *eap));
+void ex_py3 __ARGS((exarg_T *eap));
 void ex_py3file __ARGS((exarg_T *eap));
 void python3_buffer_free __ARGS((buf_T *buf));
 void python3_window_free __ARGS((win_T *win));