Add casts to fix strict compiler errors [-fpermissive]

When using g++ and enforcing strict compiler errors, this commit fixes the following:

mongoose.c: In function ‘char* mg_fgets(char*, size_t, file*, char**)’:
mongoose.c:2405:60: error: invalid conversion from ‘void*’ to ‘char*’ [-fpermissive]

mongoose.c: In function ‘int set_ports_option(mg_context*)’:
mongoose.c:4586:64: error: invalid conversion from ‘void*’ to ‘socket*’ [-fpermissive]

mongoose.c: In function ‘void* worker_thread(void*)’:
mongoose.c:5104:28: error: invalid conversion from ‘void*’ to ‘mg_context*’ [-fpermissive]

mongoose.c: In function ‘void* master_thread(void*)’:
mongoose.c:5220:28: error: invalid conversion from ‘void*’ to ‘mg_context*’ [-fpermissive]
mongoose.c:5235:58: error: invalid conversion from ‘void*’ to ‘pollfd*’ [-fpermissive]
Merge pull request #207 from bick4ord/master

Add casts to fix strict compiler errors [-fpermissive]
showing error string as well as numeric error on bind failure
Merge branch 'master' of ssh://github.com/valenok/mongoose
Added Lua dll example
Added request_timeout_ms
Added git analytics link
Workaround for non-compliant vsnprintf()
Make sure child closes all pipe fds when executing CGI
Added -DLUA_USE_DLOPEN, and added mongoose.o: mod_lua.c
Added mg_exec_lua_script, mg_prepare_lua_environment -> prepare_lua_environment
gcc complains about _MSC_VER being an undefined macro.
Merge pull request #211 from nigels-com/msc_ver

gcc complains about _MSC_VER being an undefined macro.
Consume \n in mg_fgets when reading from membuf.
Updated sqlite
Merge branch 'master' of ssh://github.com/valenok/mongoose
changed signature for mg_exec_lua_script(). fixed lua_error_handler()
(mg_fgets) Accept lines at the end not terminated by \n
(mg_fgets) Don't consume more than size bytes when line cannot fit into buffer.
Merge pull request #212 from pas2k/master

Consume \n in mg_fgets when reading from membuf
Update UserManual.md

SheBang wikipedia link is broken due to the end parenthesis. I tried escaping it with backslash and it seems to be working now.