lib-compression: Remove xz/lzma write support

For now, we keep the read support to allow for a more gradual migration from
lzma/xz.

The code has bugs.  Additionally, there is no benefit in keeping it around.
bzip2 or zstd (at maximum compression level) are likely better choices for
archival.  For non-archival usecases, a light compression algorithm like
zstd (at low to medium compression level) or lz4 are better choices.

configure.ac

@@ -172,7 +172,7 @@ AS_HELP_STRING([--with-bzlib], [Build with bzlib compression support (auto)]),
   want_bzlib=auto)
 
 AC_ARG_WITH(lzma,
-AS_HELP_STRING([--with-lzma], [Build with LZMA compression support (auto)]),
+AS_HELP_STRING([--with-lzma], [Build with LZMA decompression support (auto)]),
   TEST_WITH(lzma, $withval),
   want_lzma=auto)
 

run-test-valgrind.supp

@@ -4,17 +4,6 @@
    fun:malloc
    obj:*/bash
 }
-{
-   <liblzma>
-   Memcheck:Cond
-   obj:/lib/x86_64-linux-gnu/liblzma.so.5.*
-   obj:/lib/x86_64-linux-gnu/liblzma.so.5.*
-   obj:/lib/x86_64-linux-gnu/liblzma.so.5.*
-   obj:/lib/x86_64-linux-gnu/liblzma.so.5.*
-   obj:/lib/x86_64-linux-gnu/liblzma.so.5.*
-   fun:lzma_stream_encoder
-   fun:lzma_easy_encoder
-}
 {
    <openssl_centos6_i386_v1_0_1_compression_methods>
    Memcheck:Leak

src/lib-compression/Makefile.am

@@ -13,7 +13,6 @@ libcompression_la_SOURCES = \
 	istream-zlib.c \
 	istream-bzlib.c \
 	istream-zstd.c \
-	ostream-lzma.c \
 	ostream-lz4.c \
 	ostream-zlib.c \
 	ostream-bzlib.c \

src/lib-compression/compression.c

@@ -19,7 +19,6 @@
 #endif
 #ifndef HAVE_LZMA
 #  define i_stream_create_lzma NULL
-#  define o_stream_create_lzma NULL
 #endif
 #ifndef HAVE_LZ4
 #  define i_stream_create_lz4 NULL
@@ -162,7 +161,7 @@ const struct compression_handler compression_handlers[] = {
 	{ "deflate", NULL, NULL,
 	  i_stream_create_deflate, o_stream_create_deflate },
 	{ "xz", ".xz", is_compressed_xz,
-	  i_stream_create_lzma, o_stream_create_lzma },
+	  i_stream_create_lzma, NULL },
 	{ "lz4", ".lz4", is_compressed_lz4,
 	  i_stream_create_lz4, o_stream_create_lz4 },
 	{ "zstd", ".zstd", is_compressed_zstd,

src/lib-compression/ostream-zlib.h

@@ -4,7 +4,6 @@
 struct ostream *o_stream_create_gz(struct ostream *output, int level);
 struct ostream *o_stream_create_deflate(struct ostream *output, int level);
 struct ostream *o_stream_create_bz2(struct ostream *output, int level);
-struct ostream *o_stream_create_lzma(struct ostream *output, int level);
 struct ostream *o_stream_create_lz4(struct ostream *output, int level);
 struct ostream *o_stream_create_zstd(struct ostream *output, int level);
 

src/lib-compression/test-compression.c

@@ -730,6 +730,7 @@ static void test_compression_int(bool autodetect)
 
 	for (i = 0; compression_handlers[i].name != NULL; i++) {
 		if (compression_handlers[i].create_istream != NULL &&
+		    compression_handlers[i].create_ostream != NULL &&
 		    (!autodetect ||
 		     compression_handlers[i].is_compressed != NULL)) T_BEGIN {
 			if (compression_handlers[i].is_compressed != NULL &&