add readme in tools dir

ytools_t/README.md

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+# ytools_t
+
+Set of tools containing a few functions and comparison macros. We've also redefined the basic types to standardize macros that expect a type formed from a single word.
+
+## types
+```
+TYPE_CHAR == char; TYPE_U_CHAR == unsigned char; TYPE_INT == int; 
+TYPE_U_INT == unsigned int; TYPE_L_INT == long int; TYPE_U_L_INT == unsigned long int
+TYPE_SIZE_T == size_t; TYPE_FLOAT == float; TYPE_DOUBLE == double; 
+TYPE_L_DOUBLE == long double; TYPE_STRING == char*
+```
+
+## Precision
+`PRECISION_TYPE_FLOAT,  PRECISION_TYPE_DOUBLE, PRECISION_TYPE_L_DOUBLE` values can be modified on compilation with :
+```
+-D PRECISION_TYPE_FLOAT=100000000
+-D PRECISION_TYPE_DOUBLE=100000000000 
+-D PRECISION_TYPE_L_DOUBLE=100000000000000
+```
+for example, these values are the default precision for each type.
+
+Precision values for other types are 1.
+
+