Merge branch perror into main

Reviewed-on: #6

apps/src/memeater.c

@@ -15,6 +15,6 @@ int main()
         printf("Allocating 4 MB of memory... %lx\n", (unsigned long)allocated);
         sleep(1);
     } while ((allocated = malloc(CHUNK)));
-    printf("Out of memory. (errno=%d, %s)\n", errno, strerror(errno));
+    perror("malloc");
     printf("Press any key to restart.\n");
 }

libs/libc/include/stdio.h

@@ -35,6 +35,7 @@ extern "C"
     int vsprintf(char*, const char*, va_list);
     int vsnprintf(char*, size_t, const char*, va_list);
     int puts(const char*);
+    void perror(const char*);
 
 #ifdef __cplusplus
 }

libs/libc/src/stdio.cpp

@@ -1,3 +1,4 @@
+#include <errno.h>
 #include <luna.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -78,4 +79,9 @@ extern "C"
         va_end(ap);
         return written;
     }
+    void perror(const char* s) // FIXME: Print to stderr, whenever we have an stderr.
+    {
+        if (s && *s) { printf("%s: ", s); }
+        printf("%s\n", strerror(errno));
+    }
 }