Removed ._user_heap_stack section from the Arduino reported RAM usage

Linker script defined ._user_heap_stack section to check that there
is enough RAM left.
Arduino should not report this but only the real one used.

Example for a BluePill:
.user_heap_stack section is equal to 1536 (_Min_Heap_Size+_Min_Stack_Size)
If used to compute RAM usage of blink sketch, Arduino reports: 2456 bytes
While it is not computed, it reports 916 bytes (=2456-1536-4(align))

Linker always ensures there is enough space defined thanks .user_heap_stack
Arduino will report real size and will warn if sketch use more than the
default RAM usage (build.warn_data_percentage=75)

See #8

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

platform.txt

@@ -125,7 +125,7 @@ recipe.output.save_file={build.project_name}.{build.variant}.hex
 ## Compute size
 recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf"
 recipe.size.regex=^(?:\.text|\.data|\.rodata)\s+([0-9]+).*
-recipe.size.regex.data=^(?:\.data|\.bss|\._user_heap_stack)\s+([0-9]+).*
+recipe.size.regex.data=^(?:\.data|\.bss)\s+([0-9]+).*
 recipe.size.regex.eeprom=^(?:\.eeprom)\s+([0-9]+).*