patch 8.1.0743: giving error messages is not flexible

Problem:    Giving error messages is not flexible.
Solution:   Add semsg().  Change argument from "char_u *" to "char *", also
            for msg() and get rid of most MSG macros. (Ozaki Kiichi, closes
            #3302)  Also make emsg() accept a "char *" argument.  Get rid of
            an enormous number of type casts.
diff --git a/src/if_python.c b/src/if_python.c
index 7319382..68444aa 100644
--- a/src/if_python.c
+++ b/src/if_python.c
@@ -685,7 +685,7 @@
     if (python3_loaded())
     {
 	if (verbose)
-	    EMSG(_("E836: This Vim cannot execute :python after using :py3"));
+	    emsg(_("E836: This Vim cannot execute :python after using :py3"));
 	return FAIL;
     }
 #endif
@@ -696,7 +696,7 @@
     if (!hinstPython)
     {
 	if (verbose)
-	    EMSG2(_(e_loadlib), libname);
+	    semsg(_(e_loadlib), libname);
 	return FAIL;
     }
 
@@ -708,7 +708,7 @@
 	    close_dll(hinstPython);
 	    hinstPython = 0;
 	    if (verbose)
-		EMSG2(_(e_loadfunc), python_funcname_table[i].name);
+		semsg(_(e_loadfunc), python_funcname_table[i].name);
 	    return FAIL;
 	}
     }
@@ -725,7 +725,7 @@
 	close_dll(hinstPython);
 	hinstPython = 0;
 	if (verbose)
-	    EMSG2(_(e_loadfunc), "PyUnicode_UCSX_*");
+	    semsg(_(e_loadfunc), "PyUnicode_UCSX_*");
 	return FAIL;
     }
 
@@ -928,7 +928,7 @@
 #ifdef DYNAMIC_PYTHON
 	if (!python_enabled(TRUE))
 	{
-	    EMSG(_("E263: Sorry, this command is disabled, the Python library could not be loaded."));
+	    emsg(_("E263: Sorry, this command is disabled, the Python library could not be loaded."));
 	    goto fail;
 	}
 #endif
@@ -960,7 +960,7 @@
 	site = PyImport_ImportModule("site");
 	if (site == NULL)
 	{
-	    EMSG(_("E887: Sorry, this command is disabled, the Python's site module could not be loaded."));
+	    emsg(_("E887: Sorry, this command is disabled, the Python's site module could not be loaded."));
 	    goto fail;
 	}
 	Py_DECREF(site);
@@ -1035,7 +1035,7 @@
 #ifndef PY_CAN_RECURSE
     if (recursive)
     {
-	EMSG(_("E659: Cannot invoke Python recursively"));
+	emsg(_("E659: Cannot invoke Python recursively"));
 	return;
     }
     ++recursive;