add support for Visual Studio 2026, remove unsupported Visual Studio 2015

Author: burgerrg

BUILDING

@@ -25,7 +25,7 @@ On Unix variants:
 
 On Windows:
 
- * Microsoft Visual Studio 2022, 2019, 2017, or 2015
+ * Microsoft Visual Studio 2026, 2022, 2019, or 2017
 
 
 GETTING STARTED
@@ -370,10 +370,8 @@ where <machine type> is one of the following:
  * ti3nt     (32-bit Intel threaded)
  * i3nt      (32-bit Intel non-threaded)
 
-If you're using Visual Studio 2022 or 2019, install "Desktop
-development with C++" on the "Workloads" tabs and the "C++ 20[xx]
-Redistributable MSMs" on the "Individual components" tab under the
-"Compilers, build tools, and runtimes" section. The `build.bat` script
+If you're using Visual Studio 2026, 2022 or 2019, install "Desktop
+development with C++" on the "Workloads" tab. The `build.bat` script
 will use `c\vs.bat` to find and set up Microsoft Visual Studio
 command-line tools automatically for <machine type>; supply `/keepvs`
 if you have set up command-line tools already so that `c\vs.bat`

c/vs.bat

@@ -7,6 +7,18 @@ set Applications=%ProgramFiles%
 :: Set up Visual Studio command line environment variables given a
 :: machine type, e.g., amd64 or x86.
 
+:: Visual Studio 2026 Enterprise
+set BATDIR=%ProgramW6432%\Microsoft Visual Studio\18\Enterprise\VC\Auxiliary\Build
+if exist "%BATDIR%\vcvarsall.bat" goto found
+
+:: Visual Studio 2026 Professional
+set BATDIR=%ProgramW6432%\Microsoft Visual Studio\18\Professional\VC\Auxiliary\Build
+if exist "%BATDIR%\vcvarsall.bat" goto found
+
+:: Visual Studio 2026 Community
+set BATDIR=%ProgramW6432%\Microsoft Visual Studio\18\Community\VC\Auxiliary\Build
+if exist "%BATDIR%\vcvarsall.bat" goto found
+
 :: Visual Studio 2022 Enterprise
 set BATDIR=%ProgramW6432%\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build
 if exist "%BATDIR%\vcvarsall.bat" goto found
@@ -51,11 +63,7 @@ if exist "%BATDIR%\vcvarsall.bat" goto found
 set BATDIR=%Applications%\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build
 if exist "%BATDIR%\vcvarsall.bat" goto found
 
-:: Visual Studio 2015
-set BATDIR=%VS140COMNTOOLS%..\..\VC
-if exist "%BATDIR%\vcvarsall.bat" goto found
-
-echo Visual Studio 2022, 2019, 2017, or 2015 must be installed.
+echo Visual Studio 2026, 2022, 2019, or 2017 must be installed.
 exit 1
 
 :found