Add a few more sources to CONV_SRCS.
Turn off -Werror by default.

It inteferes with development activities by breaking your build in the
middle of a refactor.  Instead, let's enable -Werror on the Travis CI
builds via a TRAVIS_CI_BUILD option.
Refactor: Redefine `Map(T)` as a more generic `Map(T, U)` macro

To replace `Map(T)`, a new macro `PMap(T)` was defined as `Map(T, ptr_t)` for
writing maps that store pointers with less boilerplate
Merge branch 'generic-key-value-map'
API: Refactor: Rename find_{buffer,window,tabpage}

They were renamed to find_{buffer,window,tabpage}_by_handle to avoid conflicts
with existing functions of the same name.
API: Refactor: Change type of event data to `Object` from `typval_T`
API: Refactor: Enable usage of Arrays and Dictionaries as [k]vectors

- Rename a/n/m to items/size/capactity in kvec.h
- Add capactity field to Arrays/Dictionaries
API: Refactor: Add helper macros for dealing with API type casts
API: Events: Implement the 'redraw:tabs' event
API: Events: Implement the 'redraw:insert_line' event
API: Events: Implement the 'redraw:delete_line' event
API: Events: Implement the 'redraw:update_line' event