Docs: Update INSTALL and also add new prohibited options to PACKAGERS.

INSTALL

@@ -316,6 +316,18 @@ XZ Utils Installation
                             | xz -v -0 -Csha256 > foo.xz
                         time xz --test foo.xz
 
+    --disable-microlzma
+                Don't build MicroLZMA encoder and decoder. This omits
+                lzma_microlzma_encoder() and lzma_microlzma_decoder()
+                API functions from liblzma. These functions are needed
+                by specific applications only. They were written for
+                erofs-utils but they may be used by others too.
+
+    --disable-lzip-decoder
+                Disable decompression support for .lz (lzip) files.
+                This omits the API function lzma_lzip_decoder() from
+                liblzma and .lz support from the xz tool.
+
     --disable-xz
     --disable-xzdec
     --disable-lzmadec
@@ -359,15 +371,32 @@ XZ Utils Installation
                 code.
 
     --enable-unaligned-access
-                Allow liblzma to use unaligned memory access for 16-bit
+                Allow liblzma to use unaligned memory access for 16-bit,
-                and 32-bit loads and stores. This should be enabled only
+                32-bit, and 64-bit loads and stores. This should be
-                when the hardware supports this, i.e. when unaligned
+                enabled only when the hardware supports this, that is,
-                access is fast. Some operating system kernels emulate
+                when unaligned access is fast. Some operating system
-                unaligned access, which is extremely slow. This option
+                kernels emulate unaligned access, which is extremely
-                shouldn't be used on systems that rely on such emulation.
+                slow. This option shouldn't be used on systems that
+                rely on such emulation.
 
                 Unaligned access is enabled by default on x86, x86-64,
-                and big endian PowerPC.
+                big endian PowerPC, some ARM, and some ARM64 systems.
+
+    --enable-unsafe-type-punning
+                This enables use of code like
+
+                    uint8_t *buf8 = ...;
+                    *(uint32_t *)buf8 = ...;
+
+                which violates strict aliasing rules and may result
+                in broken code. There should be no need to use this
+                option with recent GCC or Clang versions on any
+                arch as just as fast code can be generated in a safe
+                way too (using __builtin_assume_aligned + memcpy).
+
+                However, this option might improve performance in some
+                other cases, especially with old compilers (for example,
+                GCC 3 and early 4.x on x86, GCC < 6 on ARMv6 and ARMv7).
 
     --enable-small
                 Reduce the size of liblzma by selecting smaller but
@@ -456,6 +485,10 @@ XZ Utils Installation
                                 sandboxing. If no Capsicum support
                                 is found, configure will give an error.
 
+                        pledge  Use pledge(2) (OpenBSD >= 5.9) for
+                                sandboxing. If pledge(2) isn't found,
+                                configure will give an error.
+
     --enable-symbol-versions
                 Use symbol versioning for liblzma. This is enabled by
                 default on GNU/Linux, other GNU-based systems, and
@@ -518,7 +551,7 @@ XZ Utils Installation
         liblzma, pass --enable-small to configure.
 
       - Tell the compiler to optimize for size instead of speed.
-        E.g. with GCC, put -Os into CFLAGS.
+        For example, with GCC, put -Os into CFLAGS.
 
       - xzdec and lzmadec will never use multithreading capabilities of
         liblzma. You can avoid dependency on libpthread by passing

PACKAGERS

@@ -138,6 +138,8 @@ Information to packagers of XZ Utils
         --enable-checks
         --enable-small (*)
         --disable-threads (*)
+        --disable-microlzma (*)
+        --disable-lzip-decoder (*)
 
     (*) These are OK when building xzdec and lzmadec as described
         in INSTALL.