Avoid moving point while analyzing text conversion

Avoid moving point while analyzing text conversion

* lisp/simple.el (analyze-text-conversion): If neither calling
p-s-i-h nor calling p-t-c-h yields a change to point, return it
to its location before analyze-text-conversion was called.

* src/keyboard.c (kbd_buffer_get_event): See that text
conversion events are uniformly delivered prior to keyboard
events arriving in unison.