#42 print_string_ptr unsafe on platforms with signed char

[Joel Klinghed]

print_string_ptr uses escapable[*ptr++] where ptr is a const char* ptr.
escapable is defined as:
static int escapable[256];

On a platform where char is signed escapable[*ptr++] might access memory infront of the escapable array as char goes from -128 to 127

[Dave Gamble]

Quite right. Fixed in svn rev68 and current files.