Tier1: add V_IsAllDigit()

This function checks if a string consists of only numeric characters.

src/public/tier1/strtools.h

@@ -67,6 +67,7 @@ const char* V_strnchr(const char* pStr, char c, ssize_t n);
 bool V_isspace(int c);
 
 inline bool V_isalnum(char c) { return isalnum((unsigned char)c) != 0; }
+bool V_IsAllDigit(const char* pString);
 
 // this is locale-unaware and therefore faster version of standard isdigit()
 // It also avoids sign-extension errors.

src/tier1/strtools.cpp

@@ -242,6 +242,21 @@ bool V_isspace(int c)
 #endif
 }
 
+bool V_IsAllDigit(const char* pString)
+{
+	while (*pString)
+	{
+		if (!V_isdigit(*pString))
+		{
+			return false;
+		}
+
+		pString++;
+	}
+
+	return true;
+}
+
 //-----------------------------------------------------------------------------
 // Purpose: 
 // Input  : *in -