On a way to factoring out OpenSSL support to a standalone file to ease
addition of other crypto libraries support in the future, move helpers
providing SHA1 calculation to crypto-utils.{c,h}. OpenSSL-related
functionality (SHA1 context management) is moved to crypto-utils-openssl.c.
Add new tr_sha1_ctx_t type and functions to be implemented by crypto
backends:
* tr_sha1_init - allocate SHA1 context and and initialize it,
* tr_sha1_update - hash some [more] data,
* tr_sha1_final - finish hash calculation and free the context.
Add new files to CMakeLists.txt (leftover from previous commit) to fix
CMake-based configuration.
On a way to factoring out OpenSSL support to a standalone file to ease
addition of other crypto libraries support in the future, move helpers
providing random numbers/data generation to crypto-utils.{c,h}. OpenSSL-
related functionality (generation of cryptographically strong random
data) is moved to crypto-utils-openssl.c.
Rename functions to follow currently accepted style:
* tr_cryptoRandBuf -> tr_rand_buffer
* tr_cryptoRandInt -> tr_rand_int
* tr_cryptoWeakRandInt -> tr_rand_int_weak
Fix rare case of invalid value being returned from tr_rand_int. Return
value for abs(INT_MIN) may be undefined and thus negative, and so
tr_rand_int will return negative value which is incorrect (out of
requested and expected range).
