rgw/rgw_formats.cc: fix realloc memory leak

Fix handling of realloc. If realloc() fails it returns NULL, assigning
the return value of realloc() directly to the pointer without checking
for the result will lead to a memory leak in error case.

Use a temporary pointer to hold the result of realloc(). In error case
print error and exit, otherwise assign it to the pointer we want to realloc.

Fix also error checks for malloc to fail as soon as malloc fails and
don't try to run realloc again after failed malloc.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
msg/async/Event.cc: use static_cast instead of c-style cast

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>