[io] Suppress fallthrough warnings

[SergioRAgostinho]

$ ninja  pcl_io                                                                                                    
[15/62] Building CXX object io/CMakeFiles/pcl_io.dir/src/lzf.cpp.o                                                                                                
../io/src/lzf.cpp: In function ‘unsigned int pcl::lzfDecompress(const void*, unsigned int, void*, unsigned int)’:                                                 
../io/src/lzf.cpp:309:24: warning: this statement may fall through [-Wimplicit-fallthrough=]                                                                      
         case 32: *op++ = *ip++; case 31: *op++ = *ip++; case 30: *op++ = *ip++; case 29: *op++ = *ip++;                                                          
                  ~~~~~~^~~~~~~                                                                                                                                   
../io/src/lzf.cpp:309:33: note: here                                                                                                                              
         case 32: *op++ = *ip++; case 31: *op++ = *ip++; case 30: *op++ = *ip++; case 29: *op++ = *ip++;                                                          
                                 ^~~~                                                                                                                             
../io/src/lzf.cpp:309:48: warning: this statement may fall through [-Wimplicit-fallthrough=]                                                                      
         case 32: *op++ = *ip++; case 31: *op++ = *ip++; case 30: *op++ = *ip++; case 29: *op++ = *ip++;                                                          
                                          ~~~~~~^~~~~~~                                                 

[taketwo]

My God 😆