Change Merlin 32 output suffix

We append an assembler identifier to generated code.  For Merlin 32,
this was "_Merlin32".  All of the other assemblers use a lower-case
string, which makes Merlin look a little weird, so it has been
changed to "_merlin32".

Windows filesystems are generally case-insensitive, so this won't
likely affect anything.

.gitignore

@@ -7,7 +7,7 @@
 SourceGen/SourceGen-settings
 SourceGen/PluginDllCache
 DIST_Debug
-DIST_release
+DIST_Release
 
 
 # User-specific files

SourceGen/AsmGen/AsmMerlin32.cs

@@ -31,7 +31,7 @@ namespace SourceGen.AsmGen {
     /// (https://www.brutaldeluxe.fr/products/crossdevtools/merlin/).
     /// </summary>
     public class GenMerlin32 : IGenerator {
-        private const string ASM_FILE_SUFFIX = "_Merlin32.S";   // must start with underscore
+        private const string ASM_FILE_SUFFIX = "_merlin32.S";   // must start with underscore
 
         // IGenerator
         public DisasmProject Project { get; private set; }