A simple execution of tmp/invoke-rename.pl

More fixes based on the compiler directives -Wcast-qual -Wwrite-strings
-Wmissing-prototypes -Wmissing-declarations. Not everything with regards
to -Wcast-qual has been fixed as some have unwanted consequences for the
rest of the code.

All symmetric cipher algorithms and hash algorithms now include support
for a POLARSSL_XXX_ALT flag that prevents the definition of the
algorithm context structure and all 'core' functions.
(cherry picked from commit 4087c470)

 - Major type rewrite of int to size_t for most variables and arguments used for buffer lengths and loops