PolarSSL: added human readable error strings

Print out human readable error strings for PolarSSL related errors
PolarSSL: changes to entropy/ctr_drbg/HAVEGE_RANDOM

Add non-threaded entropy and ctr_drbg and removed HAVEGE_RANDOM define
PolarSSL: pthread support for entropy

Added pthread support for polarssl entropy if --enable-threaded-resolver
config flag is set and pthread.h can be found.
PolarSSL: WIN32 threading support for entropy

Added WIN32 threading support for PolarSSL entropy if
--enable-threaded-resolver config flag is set and process.h can be found.
PolarSSL: Change to cURL coding style

Repaired all curl/lib/checksrc.pl warnings in the previous four patches