Use include paths relative to src/

As described in Google's style guide, the basis for Neovim's

> All of a project's header files should be listed as descendants of the
> project's source directory without use of UNIX directory shortcuts .
> (the current directory) or .. (the parent directory).

Add src as an include directory to facilitate this.

CMakeLists.txt

@@ -46,6 +46,7 @@ find_package(LibUV REQUIRED)
 include_directories(${LibUV_INCLUDE_DIRS})
 
 include_directories ("${PROJECT_BINARY_DIR}/config")
+include_directories ("${PROJECT_SOURCE_DIR}/src")
 
 set (CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 

src/os/env.c

@@ -13,8 +13,8 @@
 
 #include <uv.h>
 
-#include "os.h"
-#include "../misc2.h"
+#include "os/os.h"
+#include "misc2.h"
 
 #ifdef HAVE_CRT_EXTERNS_H
 #include <crt_externs.h>

src/os/fs.c

@@ -13,10 +13,10 @@
 
 #include <uv.h>
 
-#include "os.h"
-#include "../message.h"
-#include "../misc1.h"
-#include "../misc2.h"
+#include "os/os.h"
+#include "message.h"
+#include "misc1.h"
+#include "misc2.h"
 
 int mch_chdir(char *path) {
   if (p_verbose >= 5) {

src/os/mem.c

@@ -13,7 +13,7 @@
 
 #include <uv.h>
 
-#include "os.h"
+#include "os/os.h"
 
 /*
  * Return total amount of memory available in Kbyte.

src/os/os.h

@@ -1,7 +1,7 @@
 #ifndef NEOVIM_OS_OS_H
 #define NEOVIM_OS_OS_H
 
-#include "../vim.h"
+#include "vim.h"
 
 long_u mch_total_mem(int special);
 int mch_chdir(char *path);

src/os/users.c

@@ -13,9 +13,9 @@
 
 #include <uv.h>
 
-#include "os.h"
-#include "../garray.h"
-#include "../misc2.h"
+#include "os/os.h"
+#include "garray.h"
+#include "misc2.h"
 #ifdef HAVE_PWD_H
 # include <pwd.h>
 #endif