fileio_types.h : avoid dependency on mem.h

fileio_types.h cannot be parsed by itself
because it relies on basic types defined in `lib/common/mem.h`.
As for #3231, it likely wasn't detected because `mem.h` was probably included before within target files.
But this is not proper.

A "easy" solution would be to add the missing include,
but each dependency should be considered "bad" by default,
and only allowed if it brings some tangible value.

In this case, since these types are only used to declare internal structure variables
which are effectively only flags,
I believe it's really not valuable to add a dependency on `mem.h` for this purpose
while the standard `int` type can do the same job.

I was expecting some compiler warnings following this change,
but it turns out we don't use `-Wconversion` by default on `zstd` source code,
so there is none.

Nevertheless, I enabled `-Wconversion` locally and proceeded to fix a few conversion warnings in the process.

Adding `-Wconversion` to the list of flags used for `zstd` is something I would be favorable over the long term,
but it cannot be done overnight,
because the nb of places where this warning is triggered is daunting.
Better progressively reduce the nb of triggered `-Wconversion` warnings before enabling this flag by default.

programs/fileio.c

@@ -338,7 +338,7 @@ void FIO_setCompressionType(FIO_prefs_t* const prefs, FIO_compressionType_t comp
 
 void FIO_overwriteMode(FIO_prefs_t* const prefs) { prefs->overwrite = 1; }
 
-void FIO_setSparseWrite(FIO_prefs_t* const prefs, unsigned sparse) { prefs->sparseFileSupport = sparse; }
+void FIO_setSparseWrite(FIO_prefs_t* const prefs, int sparse) { prefs->sparseFileSupport = sparse; }
 
 void FIO_setDictIDFlag(FIO_prefs_t* const prefs, int dictIDFlag) { prefs->dictIDFlag = dictIDFlag; }
 
@@ -371,7 +371,7 @@ void FIO_setOverlapLog(FIO_prefs_t* const prefs, int overlapLog){
     prefs->overlapLog = overlapLog;
 }
 
-void FIO_setAdaptiveMode(FIO_prefs_t* const prefs, unsigned adapt) {
+void FIO_setAdaptiveMode(FIO_prefs_t* const prefs, int adapt) {
     if ((adapt>0) && (prefs->nbWorkers==0))
         EXM_THROW(1, "Adaptive mode is not compatible with single thread mode \n");
     prefs->adaptiveMode = adapt;
@@ -453,7 +453,7 @@ void FIO_setContentSize(FIO_prefs_t* const prefs, int value)
     prefs->contentSize = value != 0;
 }
 
-void FIO_setAsyncIOFlag(FIO_prefs_t* const prefs, unsigned value) {
+void FIO_setAsyncIOFlag(FIO_prefs_t* const prefs, int value) {
 #ifdef ZSTD_MULTITHREAD
     prefs->asyncIO = value;
 #else
@@ -1306,7 +1306,7 @@ FIO_compressZstdFrame(FIO_ctx_t* const fCtx,
                 windowLog = ZSTD_WINDOWLOG_LIMIT_DEFAULT;
             } else {
                 const ZSTD_compressionParameters cParams = ZSTD_getCParams(compressionLevel, fileSize, 0);
-                windowLog = cParams.windowLog;
+                windowLog = (int)cParams.windowLog;
             }
         }
         windowSize = UTIL_makeHumanReadableSize(MAX(1ULL, MIN(1ULL << windowLog, pledgedSrcSize)));
@@ -1726,14 +1726,15 @@ FIO_compressFilename_srcFile(FIO_ctx_t* const fCtx,
     return result;
 }
 
-static const char* checked_index(const char* options[], size_t length, size_t index) {
+static const char*
+checked_index(const char* options[], size_t length, size_t index) {
     assert(index < length);
     /* Necessary to avoid warnings since -O3 will omit the above `assert` */
     (void) length;
     return options[index];
 }
 
-#define INDEX(options, index) checked_index((options), sizeof(options)  / sizeof(char*), (index))
+#define INDEX(options, index) checked_index((options), sizeof(options)  / sizeof(char*), (size_t)(index))
 
 void FIO_displayCompressionParameters(const FIO_prefs_t* prefs) {
     static const char* formatOptions[5] = {ZSTD_EXTENSION, GZ_EXTENSION, XZ_EXTENSION,