patch 9.1.1732: filetype: .inc file detection can be improved

Problem:  filetype: .inc file detection can be improved
Solution: Update filetype detection for Pascal and BitBake code
          (Martin Schwan).

Fix the detection of .inc files containing Pascal and BitBake code:

- the concatenated string, merged from three lines, only contains one
  beginning and the pattern "^" would not match as expected. Use a range()
  loop to iterate each line string individually. This way, the pattern "^"
  works for beginning of lines.

- improve BitBake include file detection by also matching forward-slashes
  "/" in variable names and assignment operators with a dot ".=" and "=.".
  Valid examples, which should match, are:

    PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"
    MACHINEOVERRIDES =. "qemuall:"
    BBPATH .= ":${LAYERDIR}"

- parse twenty instead of just three lines, to accommodate for potential
  comments at the beginning of files

closes: #18202

Signed-off-by: Martin Schwan <m.schwan@phytec.de>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_filetype.vim

@@ -2694,6 +2694,21 @@ func Test_inc_file()
   call assert_equal('bitbake', &filetype)
   bwipe!
 
+  call writefile(['PREFERRED_PROVIDER_virtual/kernel = "linux-yocto"'], 'Xfile.inc')
+  split Xfile.inc
+  call assert_equal('bitbake', &filetype)
+  bwipe!
+
+  call writefile(['MACHINEOVERRIDES =. "qemuall:"'], 'Xfile.inc')
+  split Xfile.inc
+  call assert_equal('bitbake', &filetype)
+  bwipe!
+
+  call writefile(['BBPATH .= ":${LAYERDIR}"'], 'Xfile.inc')
+  split Xfile.inc
+  call assert_equal('bitbake', &filetype)
+  bwipe!
+
   " asm
   call writefile(['asmsyntax=foo'], 'Xfile.inc')
   split Xfile.inc

src/version.c

@@ -724,6 +724,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1732,
 /**/
     1731,
 /**/