[notmuch] Mac OS X/Darwin compatibility issues

[Jjgod Jiang]

Hi,

When I tried to compile notmuch under Mac OS X 10.6, several issues
arisen:

1. g++ reports 'warning: command line option "-Wmissing-declarations"
is valid for C/ObjC but not for C++'

2.
notmuch-reply.c: In function ‘address_is_users’:
notmuch-reply.c:87: warning: passing argument 2 of
‘notmuch_config_get_user_other_email’ from incompatible pointer type

That's due to the size incompatibility of 'unsigned int' and 'size_t'
(size_t is uint64_t in Mac OS X).

3. Several errors about missing GNU extensions like getline() and strndup():

warning: implicit declaration of function ‘getline’
error: ‘strndup’ was not declared in this scope

We can implement these with fgets() and strncpy() though.

- Jiang