Fix deprecation: sprintf → snprintf

[amomchilov]

sprintf is marked deprecated in the macOS clang toolchain.

It's a good idea to use snprintf anyway, to make sure we don't overflow these small buffers.

external/ragel_v6.10/ragel/parsetree.cpp:185:3: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
                sprintf( actName, "store%i", lmi->longestMatchId );
                ^
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:180:1: note: 'sprintf' has been explicitly marked deprecated here
__deprecated_msg("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead.")
^
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/cdefs.h:218:48: note: expanded from macro '__deprecated_msg'
        #define __deprecated_msg(_msg) __attribute__((__deprecated__(_msg)))
                                                      ^
external/ragel_v6.10/ragel/parsetree.cpp:198:3: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
                sprintf( actName, "last%i", lmi->longestMatchId );
                ^
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:180:1: note: 'sprintf' has been explicitly marked deprecated here
__deprecated_msg("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead.")
^
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/cdefs.h:218:48: note: expanded from macro '__deprecated_msg'
        #define __deprecated_msg(_msg) __attribute__((__deprecated__(_msg)))
                                                      ^
external/ragel_v6.10/ragel/parsetree.cpp:212:3: warning: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Wdeprecated-declarations]
                sprintf( actName, "next%i", lmi->longestMatchId );
                ^
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/stdio.h:180:1: note: 'sprintf' has been explicitly marked deprecated here
__deprecated_msg("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead.")
^