Fix GCC's -Wuninitialized warnings

Fix the issues found by GCC when the -Wuninitialized flag is specified.
Fix GCC's -Wimplicit-function-declaration warnings

Fix the issues found by GCC when the -Wimplicit-function-declaration
flag is specified.
Move global variables from .h to .c files

Simplify things by moving the definition of global variables into .c
files, where they belong.
Don't mark SSL_METHOD variable as "const"

The SSL_CTX_new(3) function expects a non-"const" SSL_METHOD value.