Removed syntastic and replaced it with ale

Read more here:
https://github.com/w0rp/ale

sources_non_forked/ale/ale_linters/glsl/glslang.vim

@@ -0,0 +1,46 @@
+" Author: Sven-Hendrik Haase <svenstaro@gmail.com>
+" Description: glslang-based linter for glsl files
+"
+" TODO: Once https://github.com/KhronosGroup/glslang/pull/1047 is accepted,
+" we can use stdin.
+
+let g:ale_glsl_glslang_executable =
+\ get(g:, 'ale_glsl_glslang_executable', 'glslangValidator')
+
+let g:ale_glsl_glslang_options = get(g:, 'ale_glsl_glslang_options', '')
+
+function! ale_linters#glsl#glslang#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'glsl_glslang_executable')
+endfunction
+
+function! ale_linters#glsl#glslang#GetCommand(buffer) abort
+    return ale_linters#glsl#glslang#GetExecutable(a:buffer)
+    \   . ' ' . ale#Var(a:buffer, 'glsl_glslang_options')
+    \   . ' ' . '-C %t'
+endfunction
+
+function! ale_linters#glsl#glslang#Handle(buffer, lines) abort
+    " Matches patterns like the following:
+    "
+    " ERROR: 0:5: 'foo' : undeclared identifier
+    let l:pattern = '^\(.\+\): \(\d\+\):\(\d\+\): \(.\+\)'
+    let l:output = []
+
+    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+        call add(l:output, {
+        \   'lnum': str2nr(l:match[3]),
+        \   'col': str2nr(l:match[2]),
+        \   'text': l:match[4],
+        \   'type': l:match[1] is# 'ERROR' ? 'E' : 'W',
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+call ale#linter#Define('glsl', {
+\   'name': 'glslang',
+\   'executable_callback': 'ale_linters#glsl#glslang#GetExecutable',
+\   'command_callback': 'ale_linters#glsl#glslang#GetCommand',
+\   'callback': 'ale_linters#glsl#glslang#Handle',
+\})

sources_non_forked/ale/ale_linters/glsl/glslls.vim

@@ -0,0 +1,38 @@
+" Author: Sven-Hendrik Haase <svenstaro@gmail.com>
+" Description: A language server for glsl
+
+call ale#Set('glsl_glslls_executable', 'glslls')
+call ale#Set('glsl_glslls_logfile', '')
+
+function! ale_linters#glsl#glslls#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'glsl_glslls_executable')
+endfunction
+
+function! ale_linters#glsl#glslls#GetCommand(buffer) abort
+    let l:executable = ale_linters#glsl#glslls#GetExecutable(a:buffer)
+    let l:logfile = ale#Var(a:buffer, 'glsl_glslls_logfile')
+    let l:logfile_args = ''
+    if l:logfile isnot# ''
+        let l:logfile_args = ' --verbose -l ' . l:logfile
+    endif
+    return ale#Escape(l:executable) . l:logfile_args . ' --stdin'
+endfunction
+
+function! ale_linters#glsl#glslls#GetLanguage(buffer) abort
+    return 'glsl'
+endfunction
+
+function! ale_linters#glsl#glslls#GetProjectRoot(buffer) abort
+    let l:project_root = ale#c#FindProjectRoot(a:buffer)
+
+    return !empty(l:project_root) ? fnamemodify(l:project_root, ':h:h') : ''
+endfunction
+
+call ale#linter#Define('glsl', {
+\   'name': 'glslls',
+\   'lsp': 'stdio',
+\   'executable_callback': 'ale_linters#glsl#glslls#GetExecutable',
+\   'command_callback': 'ale_linters#glsl#glslls#GetCommand',
+\   'language_callback': 'ale_linters#glsl#glslls#GetLanguage',
+\   'project_root_callback': 'ale_linters#glsl#glslls#GetProjectRoot',
+\})