LibC: Add drand48, srand48

These functions are required for the `perl5` port's random function to
operate correctly. As a bonus, this allows us to remove a nasty patch
that replaces `drand48` with `random`.

Userland/Libraries/LibC/stdlib.h

@@ -78,6 +78,8 @@ __attribute__((noreturn)) void _Exit(int status);
 #define RAND_MAX 32767
 int rand(void);
 void srand(unsigned seed);
+double drand48(void);
+void srand48(long seed);
 
 long int random(void);
 void srandom(unsigned seed);